Semiconductor device

ABSTRACT

p-type wells are provided within an n-type embedded well of a semiconductor substrate lying in an area for forming a flash memory, in a state of being isolated from one another. A capacitance section, a data write/erase charge injection/discharge section and a data read MIS•FET are disposed in each of the p-type wells. The capacitance section is disposed between the data write/erase charge injection/discharge section and the data read MIS•FET. In the data write/erase charge injection/discharge section, writing and erasing of data by an FN tunnel current at a channel entire surface are performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese patent application No. 2006-172115 filed onJun. 22, 2006 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device technique, andparticularly to a technique effective when applied to a semiconductordevice having a nonvolatile memory circuit section.

Of semiconductor devices, there is known one that has thereinside anonvolatile memory circuit section for storing relatively small-capacityinformation such as information used upon trimming, relief and imageadjustments of an LCD (Liquid Crystal Device), information about theproduction number of a semiconductor device, etc.

This semiconductor device having the nonvolatile memory circuit sectionhas been described in, for example, Japanese Unexamined PatentPublication No. 2006-80247 (refer to a patent document 1). The followingconfiguration of nonvolatile memory cell has been disclosed in thepatent document 1. A floating gate electrode for storing an electriccharge that contributes to storage of information is disposed in a mainsurface of a semiconductor substrate. The floating gate electrode has aportion relatively broad in width and a portion relatively narrow inwidth. The relatively broad portion of the floating gate electrode formsan electrode for a capacitive element. Part of the relatively narrowportion of the floating gate electrode serves as a gate electrode of aninformation write field effect transistor. Other part of the relativelynarrow portion of the floating gate electrode serves as a gate electrodeof an information read field effect transistor.

Further, a configuration in which a capacitance section, a writetransistor and a read transistor are isolated by n wells, has beendisclosed in, for example, FIG. 7 of U.S. Pat. No. 6,788,574 (patentdocument 2). A configuration in which write/erase is performed by an FNtunnel current has been disclosed in FIGS. 4A through 4C and columns 6-7in the patent document 2.

SUMMARY OF THE INVENTION

However, there has recently been a tendency that the memory capacity ofthe nonvolatile memory circuit section provided in the semiconductordevice also increases. Therefore, an important problem is how to reducethe occupied area of the nonvolatile memory circuit section while largermemory capacity is being ensured, in such a manner that the area oflaying out the nonvolatile memory circuit section does not bringpressure to bear on the area of laying out a main circuit.

Thus, an object of the present invention is to provide a techniquecapable of reducing the area of a nonvolatile memory circuit sectionprovided in a semiconductor device.

The above, other objects and novel features of the present inventionwill become apparent from the description of the present specificationand the accompanying drawings.

A summary of a typical or representative one of the inventions disclosedin the present application will briefly be explained as follows:

The present invention provides a nonvolatile memory cell having a dataread transistor, a capacitive element and a data write/erase element. Inthe nonvolatile memory cell, the data read transistor and the datawrite/erase element are disposed away from each other by the capacitiveelement disposed therebetween. A first electrode of the capacitiveelement, a second electrode of the data read transistor and a thirdelectrode of the data write/erase element are constituted of part of acommon floating gate electrode extending along the direction in whichthe data read transistor, the capacitive element and the datawrite/erase element are arranged. The second electrode of the data readtransistor and the third electrode of the data write/erase element arespaced away from each other by the first electrode of the capacitiveelement disposed therebetween.

Advantageous effects obtained by a representative one of the inventionsdisclosed in the present application will be described briefly asfollows:

In a nonvolatile memory cell having a data read transistor, a capacitiveelement and a data write/erase element, the data read transistor and thedata write/erase element are disposed away from each other by thecapacitive element disposed therebetween. A first electrode of thecapacitive element, a second electrode of the data read transistor and athird electrode of the data write/erase element are constituted of partof a common floating gate electrode extending along the direction inwhich the data read transistor, the capacitive element and the datawrite/erase element are arranged. The second electrode of the data readtransistor and the third electrode of the data write/erase element arespaced away from each other by the first electrode of the capacitiveelement disposed therebetween. Thus, the area of a nonvolatile memorycircuit section provided in a semiconductor device can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary plan view showing memory cells corresponding toone bit of a flash memory for a semiconductor device discussed by thepresent inventors;

FIG. 2 is a plan view of a memory cell array where the memory cellsshown in FIG. 1 are respectively brought to a one bit/one cellconfiguration;

FIG. 3 is a plan view of a flash memory for a semiconductor deviceillustrative of a first embodiment of the present invention;

FIG. 4 is a fragmentary enlarged plan view of the flash memory shown inFIG. 3;

FIG. 5 is a cross-sectional view taken along line Y1-Y1 of FIG. 3;

FIG. 6 is a cross-sectional view taken along line X1-X1 of FIG. 4;

FIG. 7 is a cross-sectional view taken along line X2-X2 of FIG. 4;

FIG. 8 is a cross-sectional view taken along line X3-X3 of FIG. 4;

FIG. 9 is a cross-sectional view of a high breakdown section of a maincircuit unit employed in the semiconductor device illustrative of thefirst embodiment of the present invention;

FIG. 10 is a cross-sectional view of a low breakdown section of the maincircuit unit employed in the semiconductor device illustrative of thefirst embodiment of the present invention;

FIG. 11 is a fragmentary circuit diagram of the flash memory shown inFIG. 3;

FIG. 12 is a circuit diagram showing voltages applied to respectiveparts at a data write operation of the flash memory shown in FIG. 11;

FIG. 13 is a circuit diagram illustrating voltages applied to therespective parts at a data batch-erase operation of the flash memoryshown in FIG. 11;

FIG. 14 is a circuit diagram depicting voltages applied to therespective parts at a data-bit unit erase operation of the flash memoryshown in FIG. 11;

FIG. 15 is a circuit diagram showing voltages applied to the respectiveparts at a data read operation of the flash memory shown in FIG. 11;

FIG. 16 is a cross-sectional view taken along line Y1-Y1 at the datawrite operation of the flash memory shown in FIG. 3;

FIG. 17 is a cross-sectional view taken along line Y1-Y1 at the dataerase operation of the flash memory shown in FIG. 3;

FIG. 18 is a cross-sectional view taken along line Y1-Y1 at the dataread operation of the flash memory shown in FIG. 3;

FIG. 19 is a plan view of a flash memory for a semiconductor deviceillustrative of a second embodiment of the present invention;

FIG. 20 is a fragmentary enlarged plan view of the flash memory shown inFIG. 19;

FIG. 21 is a cross-sectional view taken along line Y2-Y2 of FIG. 19;

FIG. 22 is a cross-sectional view taken along line X1-X1 of FIG. 20;

FIG. 23 is a cross-sectional view taken along line X2-X2 of FIG. 20;

FIG. 24 is a cross-sectional view taken along line X3-X3 of FIG. 20;

FIG. 25 is a fragmentary cross-sectional view showing a semiconductorsubstrate lying in a main circuit forming area during a process formanufacturing a semiconductor device, showing one embodiment of thepresent invention;

FIG. 26 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in a flash memory forming area at the same manufacturingprocess as FIG. 25;

FIG. 27 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 25;

FIG. 28 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 27;

FIG. 29 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 27;

FIG. 30 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 29;

FIG. 31 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 29;

FIG. 32 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 31;

FIG. 33 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 31;

FIG. 34 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 33;

FIG. 35 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 33;

FIG. 36 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 35;

FIG. 37 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 35;

FIG. 38 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 37;

FIG. 39 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 37;

FIG. 40 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 39;

FIG. 41 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the main circuit forming area during thesemiconductor device manufacturing process following FIG. 39;

FIG. 42 is a fragmentary cross-sectional view showing the semiconductorsubstrate lying in the flash memory forming area at the samemanufacturing process as FIG. 41;

FIG. 43 is a plan view of a flash memory for a semiconductor deviceillustrative of a third embodiment of the present invention;

FIG. 44 is a fragmentary enlarged plan view of the flash memory shown inFIG. 43;

FIG. 45 is a cross-sectional view taken along line Y3-Y3 of FIG. 43;

FIG. 46 is a plan view showing a flash memory as one example where aplurality of the memory cells shown in FIG. 2 are arranged even in afirst direction;

FIG. 47 is a plan view of a flash memory for a semiconductor deviceillustrative of a fourth embodiment of the present invention;

FIG. 48 is a fragmentary enlarged plan view of the flash memory shown inFIG. 47;

FIG. 49 is a plan view showing an arrangement of wirings in a memorycell array of FIG. 47;

FIG. 50 is a plan view of a flash memory for a semiconductor deviceillustrative of a fifth embodiment of the present invention;

FIG. 51 is a fragmentary enlarged plan view of the flash memory shown inFIG. 50;

FIG. 52 is a cross-sectional view taken along line X4-X4 of FIG. 51;

FIG. 53 is a cross-sectional view taken along line X3-X3 of FIG. 51;

FIG. 54 is a plan view of a flash memory for a semiconductor deviceillustrative of a sixth embodiment of the present invention;

FIG. 55 is a fragmentary enlarged plan view of the flash memory shown inFIG. 54;

FIG. 56 is a cross-sectional view taken along line X5-X5 of FIG. 55;

FIG. 57 is a plan view of a flash memory for a semiconductor deviceillustrative of a seventh embodiment of the present invention; and

FIG. 58 is a fragmentary enlarged plan view of the flash memory shown inFIG. 57.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described by being divided into a plurality ofsections or embodiments whenever circumstances require it forconvenience in the following embodiments. However, unless otherwisespecified in particular, they are not irrelevant to one another. Onethereof has to do with modifications, details and supplementaryexplanations of some or all of the other. When reference is made to thenumber of elements or the like (including the number of pieces,numerical Values, quantity, range, etc.) in the following embodiments,the number thereof is not limited to a specific number and may begreater than or less than or equal to the specific number unlessotherwise specified in particular and definitely limited to the specificnumber in principle. It is also needless to say that components(including element or factor steps, etc.) employed in the followingembodiments are not always essential unless otherwise specified inparticular and considered to be definitely essential in principle.Similarly, when reference is made to the shapes, positional relationsand the like of the components or the like in the following embodiments,they will include ones substantially analogous or similar to theirshapes or the like unless otherwise specified in particular andconsidered not to be definitely so in principle, etc. This is similarlyapplied even to the above-described numerical values and range.Constituent elements each having the same function in all the drawingsfor describing the present embodiments are respectively given the samereference numerals, and their repetitive explanations will therefore beomitted where possible. Preferred embodiments of the present inventionwill hereinafter be described in detail with reference to theaccompanying drawings.

First Preferred Embodiment

FIG. 1 shows a plan view of memory cells MC0 corresponding to one bit ofa flash memory suitable for a semiconductor device discussed by thepresent inventors. Incidentally, although FIG. 1 is a plan view, partsthereof are hatched to make it easy to see the drawing. A symbol Y is afirst direction and indicates the direction in which local data linesextend. A symbol X is a second direction orthogonal to the firstdirection Y and indicates the direction in which word lines extend.

In the present configuration, the two memory cells MC0 are arranged forone bit (one bit/two cell configuration). One selection MIS•FET (MetalInsulator Semiconductor Field Effect Transistor) QS is arranged for onebit. Each of the memory cells MC0 has a data read MIS•FETQR that sharesa floating gate electrode FG, a data write/erase chargeinjection/discharge part or section CWE and a capacitance part orsection C. The data read MIS•FETQR, the data write/erase chargeinjection/discharge section CWE and the capacitance section C arearranged side by side in order from top to bottom as viewed in FIG. 1.

FIG. 2 shows a plan view of a memory cell array where the memory cellsMC0 shown in FIG. 1 are arranged in a one bit/one cell configuration.Incidentally, although FIG. 2 is a plan view, parts thereof are hatchedto make it easy to see the drawing.

The memory cells MC0 are arranged side by side in plural form along thesecond direction X. Each memory cell MC has a data read MIS•FETQR, adata write/erase charge injection/discharge section CWE, a capacitancesection C and a selection MIS•FETQS. The order of laying out the dataread MIS•FETQR, data write/erase charge injection/discharge section CWEand capacitance section C is the same as FIG. 1.

Here, it is considered that a reduction in the area of the memory cellarray results from the sharing of respective semiconductor regions forthe data read MIS•FETQR and capacitance sections C of the memory cellsMC0 adjacent to each other.

When, however, the distance between the adjacent memory cells MC0 isshortened so as to make sharing of the respective semiconductor regionsfor the data read MIS•FETQR and capacitance sections C of the adjoiningmemory cells MC0 under the configurations of the memory cells MC0 shownin FIG. 1, semiconductor regions for the charge injection/dischargesections CWE, which need isolation where the one bit/one cellconfiguration is formed by the memory cells MC0 shown in FIG. 1, alsooverlap each other.

Therefore, when the one bit/one cell configuration is formed by thememory cells MC0 shown in FIG. 1, the respective semiconductor regionsfor the data read MIS•FETQR and capacitance sections C of the memorycells MC0 adjacent to each other cannot be shared. Accordingly, aproblem arises in that the memory cells MC0 adjacent to each othershould be separated from each other and the reduction in the area of thememory cell array is impaired.

The semiconductor device according to the first embodiment will next beexplained. The semiconductor device according to the present embodimentincludes a main circuit and a flash memory (nonvolatile memory circuitsection) that stores relatively small-capacity desired informationrelated to the main circuit, both of which are formed in the samesemiconductor chip.

As the main circuit, for example, an LCD (Liquid Crystal Device) drivercircuit is formed. In this case, the desired information includes, forexample, layout address information about each effective memory cell(defect-free memory cell) and each effective LCD element used uponrelief of an LCD, adjustment voltage trimming tap information used uponan LCD image adjustment, digital information about each variableresistor, etc. An external source supplied from outside thesemiconductor device (semiconductor chip) is used as a single powersupply. A source voltage of the single power supply is 3.3V or so, forexample.

However, the main circuit is not limited to the LCD driver circuit andcan be changed in various ways. As the main circuit, there are known amemory circuit such as a DRAM (Dynamic Random Access Memory), an SRAM(Static RAM) or the like, a logical circuit such as a CPU (CentralProcessing Unit), an MPU (Micro Processing Unit) or the like, a mixedcircuit of these memory circuits and logical circuits, etc.

The desired information is not limited to the above and can be changedin various ways. As the desired information, there are known, forexample, layout address information about effective (used) elements usedupon trimming in the semiconductor chip, information about effectivememory cells (defect-free memory cells) used upon relief of the memorycircuit, trimming information for setting variations of an internalfrequency oscillator to within a desired range, information about amanagement code for each semiconductor device, information about theproduction number of the semiconductor device, etc.

The flash memory for the semiconductor device according to the firstembodiment will first be explained. FIG. 3 is a plan view of the flashmemory for the semiconductor device according to the first embodiment,FIG. 4 is a fragmentary enlarged plan view of the flash memory shown inFIG. 3, FIG. 5 is a cross-sectional view taken along line Y1-Y1 of FIG.3, FIG. 6 is a cross-sectional view taken along line X1-X1 of FIG. 4,FIG. 7 is a cross-sectional view taken along line X2-X2 of FIG. 4, andFIG. 8 is a cross-sectional view taken along line X3-X3 of FIG. 4,respectively. Incidentally, although FIGS. 3 and 4 are plan views, partsthereof are hatched to make it easy to see the drawings.

In the first embodiment, a plurality of the memory cells MC1 aredisposed side by side regularly along a second direction X in a flashmemory area of a main surface (first main surface) of a semiconductorsubstrate (hereinafter called simply “substrate”) 1S constituting asemiconductor chip. Here, one memory cell MC1 is arranged for one bit(one bit/one cell configuration).

The substrate 1S comprises, for example, a p-type (second conductiontype) silicon (Si) single crystal and has a first main surface and asecond main surface located on the sides opposite to each other alongits thickness direction.

Isolation parts TI are disposed in the first main surface of thesubstrate 1S. The isolation parts TI are parts that define activeregions L (L1, L2, L3, L4 and L5) respectively. Here, the isolationparts TI are formed as trench-type isolation parts called so-called SGI(Shallow Groove Isolation) or STI (Shallow Trench Isolation), which areformed by, for example, embedding an insulating film comprising siliconoxide or the like in shallow trenches dug in the main surface of thesubstrate 1S.

An n-type (first conduction type) embedded well (first well) DNW isformed over the substrate 1S over a desired depth as viewed from itsmain surface. And, p-type wells HPW1, HPW2, HPW3 and an n-type well HNWare respectively formed in the n-type embedded well DNW in a state inwhich they are being internally wrapped. The p-type wells HPW1, HPW2 andHPW3 are disposed in a state in which they are adjacent to one anotheralong the first direction Y. The p-type well (fourth well) HPW1 isdisposed between the p-type well (second well) HPW2 and the p-type well(third well) HPW3.

The p-type wells HPW1, HPW2 and HPW3 are electrically isolated from oneanother by the n-type well HNW and the embedded well DNW disposedbetween their adjacent wells. A plurality of the p-type wells HPW2 arealso electrically isolated from one another by the n-type well HNW andthe embedded well DNW disposed therebetween. Although the n-type wellHNW is in contact with the p-type well HPW3, the n-type well HNW is notin contact with the p-type wells HPW1 and HPW2 to ensure a breakdownvoltage, and the embedded well DNW is interposed between the n-type wellHNW and the p-type wells HPW1 and HPW2.

An impurity indicative of a p type like, for example, boron or the likeis contained in the p-type wells HPW1, HPW2 and HPW3. Further, p⁺-typesemiconductor regions 4 a are formed in upper-layer parts of the p-typewell HPW3 of these. Although the same impurity as the p-type well HPW3is contained in each of the p⁺-type semiconductor regions 4 a, theimpurity concentration of the p⁺-type semiconductor region 4 a is set soas to become higher than that of the p-type well HPW3. A silicide layer5 a like, for example, cobalt silicide (CoSi_(x)) or the like is formedover part of a surface layer of the p⁺-type semiconductor region 4 a.The p⁺-type semiconductor region 4 a is electrically coupled to aconductor part 7 a lying in a contact hole CT formed in an insultinglayer 6 provided over the main surface of the substrate 1S through thesilicide layer 5 a. The insulating layer 6 has an insulating layer 6 aand an insulating layer 6 b deposited thereover. The lower insulatinglayer 6 a comprises, for example, silicon nitride (Si₃N₄) and the upperinsulating layer 6 b comprises, for example, silicon oxide (SiO₂).

An impurity indicative of an n type like, for example, phosphor (P) orarsenic (As) is contained in the n-type well HNW. The impurityconcentration thereof is formed in a concentration higher than that ofthe embedded well DNW. n⁺-type semiconductor regions 8 a are formed inan upper-layer part of the n-type well HNW. Although the same impurityas the n-type well HNW is contained in each n⁺-type semiconductor region8 a, the impurity concentration of the n⁺-type semiconductor region 8 ais set so as to become higher than that of the n-type well HNW. Then⁺-type semiconductor region 8 a is electrically coupled to eachconductor part 7 b lying in a contact hole CT formed in the insultinglayer 6 through the silicide layer 5 a formed in part of its surfacelayer.

Each of the memory cells MC1 that constitute the flash memory accordingto the first embodiment has a floating gate electrode FG, a data readMIS•FETQ, a capacitance section C, a data write/erase chargeinjection/discharge section CWE and a selection MIS•FETQS.

The floating gate electrode FG has the function of storing an electriccharge that contributes to storage of information. The floating gateelectrode FG comprises a conductor like, for example, low-resistancepolycrystalline silicon or the like and is formed in an electricallyfloating state (in a state insulated from other conductor). Constitutingthe gate configurations of the memory cells MC1 as single layers in thisway makes it possible to facilitate matching in manufacturing betweenthe memory cells MC1 of the flash memory and the elements of the maincircuit. It is therefore possible to shorten the time required tomanufacture the semiconductor device and reduce its manufacturing cost.

Sidewalls SW comprising, for example, silicon oxide are formed over theside surfaces of the floating gate electrode FG. A cap insulating layer6 c is formed so as to cover the upper surface of the floating gateelectrode FG and the surfaces of the sidewalls SW. The cap insulatinglayer 6 c comprises, for, example, silicon oxide and is formed betweenthe upper surface of the floating gate electrode FG and the insulatinglayer 6 b in such a manner that the insulating layer 6 a comprisingsilicon nitride does not directly contact the upper surface of thefloating gate electrode FG. This results from the following reasons.That is, when the insulating layer 6 a comprising silicon nitride isdeposited by a plasma chemical vapor deposition (CVD) method or thelike, the insulating layer 6 a is easy to assume a silicon-rich film atthe early stage of its deposition. Therefore, there is a case in whichwhen the insulting layer 6 a is formed in a state of being in directcontact with the upper surface of the floating gate electrode FG, theelectric charge in the floating gate electrode FG flows into thesubstrate 1S side through the silicon-rich portion of the insulatinglayer 6 a and is discharged through the corresponding conductor part. Asa result, a data retention characteristic of the flash memory isdegraded. Forming the cap insulating layer 6 c enables suppression orprevention of such a defective condition.

The cap insulating layer 6 c is formed even over resistive elements (notshown) provided in other area of the substrate 1S. Each resistiveelement is constituted of, for example, a polycrystalline silicon filmand can be formed in accordance with the same process step as theprocess step of forming the floating gate electrode FG. Providing thecap insulating layer 6 c over such resistive elements makes it possibleto selectively make and divide an area in which the silicide layer 5 ais formed over each resistive element and an area in which no silicidelayer 5 a is formed. Thus, the resistive element having a desiredresistance value can be formed. That is, in the first embodiment, aninsulating layer for fabricating and dividing the silicide layer 5 aover the resistive elements and an insulating layer provided between thesilicide layer and the insulating layer 6 a provided over the floatinggate electrode FG are formed using the cap insulating layer 6 c inaccordance with the same process step. Thus, the respective insulatinglayers need not to be formed in discrete process steps and hence theprocess of manufacturing the semiconductor device can be simplified.

As shown in FIG. 5, the cap insulating layer 6 c covers the uppersurface of each floating gate electrode FG and the surfaces of thesidewalls SW and is formed so as to extend to over n⁺-type semiconductorregions 12 b, p⁺-type semiconductor regions 15 b and p ⁺-typesemiconductor regions 17 b to be described later. This is because thereis a high possibility that when the silicide layer 5 a grows to withinthe low-concentration n⁻-type semiconductor region 12 a, p⁻-typesemiconductor region 15 a and p ⁻-type semiconductor region 17 a uponforming the silicide layer 5 a, a junction leak current relative to thesubstrate 1S will occur. In the present application, the aboveoccurrence of junction leak can be prevented because the silicide layers5 a can be formed so as to be separated from the low-concentrationn⁻-type semiconductor regions 12 a, p⁻-type semiconductor regions 15 aand p ⁻-type semiconductor regions 17 a by the cap insulating layer 6 c.

As shown in FIGS. 3 and 4, the floating gate electrodes FG are formed ina state of extending along the first direction Y so as to planarlyoverlap with the p-type wells HPW1, HPW2 and HPW3 adjacent to oneanother along the first direction Y. That is, each of the floating gateelectrodes FG integrally has a first part which planarly overlaps withthe p-type well HPW1, a second part which extends from a first side ofthe first part to the data read MIS•FETQR along the first direction Y,and a third part which extends from a second side extending along thefirst side, of the first part to the data write/erase chargeinjection/discharge section CWE along the first direction.

Data read MIS•FETQR and selection MIS•FETQS are disposed in the p-typewell HPW3. That is, each data read MIS•FETQR is disposed in a position(second position) where the second part of the floating gate electrodeFG planarly overlaps with the active region L1 of the p-type well HPW3.The data read MIS•FETQR has a gate electrode (second electrode) FGR, agate insulting film (second insulating film) 10 b and a pair of n-typesemiconductor regions 12 and 12. A channel of the data read MIS•FETQR isformed in a surface layer of the p-type well HPW3 over which the gateelectrode FGR and the active region L1 overlap each other planarly.

The gate electrode FGR is formed of part of the floating gate electrodeFG. The gate insulating film 10 b is constituted of, for example,silicon oxide and is formed between the gate electrode FGR and thesubstrate 1S (p-type well HPW3). The thickness of the gate insulatingfilm 10 b is 13.5 nm or so, for example.

The pair of n-type semiconductor regions 12 and 12 is formed in aposition where the gate electrode FGR is interposed therebetween withinthe p-type well HPW3. The pair of n-type semiconductor regions 12 and 12respectively have n⁻-type semiconductor regions 12 a on their channelsides, and n⁺-type semiconductor regions 12 b respectively coupledthereto. Although an impurity of the same conduction type, such asphosphor (P) or arsenic (As) or the like is contained in each of then⁻-type semiconductor regions 12 a and the n⁺-type semiconductor regions12 b, the impurity concentration of the n⁺-type semiconductor region 12b is set so as to become higher than that of the n⁻-type semiconductorregion 12 a.

One (source side) of the pair of the semiconductor regions 12 and 12 isshared with one (source side) of a pair of semiconductor regions 12 fordata read MIS•FETQR of other adjoining memory cell MC1. Thesemiconductor region 12 on the source side is electrically coupled to aconductor part 7 d lying in a contact hole CT formed in the insulatinglayer 6, through the silicide layer 5 a formed in part of the surfacelayer of the n⁺-type semiconductor region 12 b. The conductor part 7 dis electrically coupled to its corresponding source line SL. On theother hand, the other of the pair of semiconductor regions 12 and 12 isshared with one of the n-type semiconductor regions 12 used for thesource and drain of the selection MIS•FETQS.

The selection MIS•FETQS has a gate electrode FGS, a gate insulating film10 e and a pair of n-type semiconductor regions 12 and 12 forsource/drain. A channel for the selection MIS•FETQS is formed in thesurface layer of the p-type well HPW3 over which the gate electrode FGSand the active region L1 overlap planarly.

The gate electrode FGS is formed of, for example, low-resistancepolycrystalline silicon. Sidewalls SW are formed even over theircorresponding side surfaces of the gate electrode FGS. The silicidelayer 5 a is formed in the surface layer of the gate electrode FGS. Thegate electrode FGS is electrically coupled to its correspondingconductor part 7 f lying in a contact hole CT formed in the insulatinglayer 6. The conductor part 7 f is electrically coupled to itscorresponding selection line GS.

The gate insulating film 10 e comprises, for example, silicon oxide andis formed between the gate electrode FGS and the substrate 1S (p-typewell HPW3). The thickness of the gate insulating film 10 e is 13.5 nm orso, for example.

The pair of n-type semiconductor regions 12 and 12 for the selectionMIS•FETQS is identical in configuration to the n-type semiconductorregions 12 for the data read MIS•FETQR. The other n-type semiconductorregion 12 for the selection MIS•FETQS is electrically coupled to itscorresponding conductor part 7 g lying in a contact hole CT defined inthe insulating layer 6, through the silicide layer 5 a formed in part ofits surface layer. The conductor part 7 g is electrically coupled to itscorresponding data read bit line RBL.

Data write/erase charge injection/discharge sections CWE are disposedfor a plurality of p-type wells HPW2. That is, each data write/erasecharge injection/discharge section CWE is disposed in a position (thirdposition) where the third part of the floating gate electrode FGplanarly overlaps with the active region L2 of the p-type well (secondwell) HPW2. The charge injection/discharge section CWE has a capacitiveelectrode (third electrode) FGC1, a capacitive insulating film (thirdinsulating film) 10 d, p-type semiconductor regions 15 and 15, and ap-type well HPW2.

The capacitive electrode FGC1 is formed of part of the floating gateelectrode FG and corresponds to a portion for forming an electrode forthe charge injection/discharge section CWE. The capacitive insulatingfilm 10 d comprises, for example, silicon oxide and is formed betweenthe capacitive electrode FGC1 and the substrate 1S (p-type well HPW2).The thickness of the capacitive insulating film 10 d ranges from, forexample, over 10 nm to under 20 nm.

In the charge injection/discharge section CWE employed in the firstembodiment, however, electrons are injected from the p-type well HPW2 tothe capacitive electrode FGC1 through the capacitive insulating film 10d, and the electrons of the capacitive electrode FGC1 are dischargedinto the p-type well HPW2 through the capacitive insulating film 10 d,upon rewriting or reprogramming of data. Therefore, the thickness of thecapacitive insulating film 10 d is set thin, described specifically, itsthickness is set to a thickness of 13.5 nm or so, for example. This isbecause when the thickness of the capacitive insulating film 10 d isthinner than 10 nm, the reliability of the capacitive insulating film 10d cannot be ensured. Further, when the thickness of the capacitiveinsulating film 10 d is made thicker than 20 nm, it becomes difficult tocause the electrons to pass therethrough, and hence the rewriting ofdata cannot be carried out successfully.

The p-type semiconductor regions 15 for each charge injection/dischargesection CWE are formed in positions where they interpose the capacitiveelectrode FGC1 therebetween within the p-type well HPW2. Thesemiconductor regions 15 respectively have p⁻-type semiconductor regions15 a on the channel side and p⁺-type semiconductor regions 15 brespectively coupled thereto. Although an impurity of the sameconduction type, such as boron (B) is contained in the p⁻-typesemiconductor regions 15 a and p ⁺-type semiconductor regions 15 b, theimpurity concentration of each p⁺-type semiconductor region 15 a is setso as to become higher than that of each p⁻-type semiconductor region 15a.

The semiconductor regions 15 on both sides of the capacitive electrodeFGC1 are both configured as a p type. However, it is also possible toconfigure one thereof as a p-type semiconductor region 15 and configurethe other (one side) thereof as an n-type semiconductor region 15. Inthis case, the semiconductor region 15 a of the other n-typesemiconductor region 15 is configured as an n⁻-type, and thesemiconductor region 15 b thereof is configured as an n⁺-type (higherthan n⁻-type in impurity concentration). Each semiconductor region canbe formed by causing the n⁻-type semiconductor region 15 a and n ⁺-typesemiconductor region 15 b to contain an impurity like arsenic (As) orphosphor (P). While the effect of providing each chargeinjection/discharge section CWE with the n⁻-type semiconductor region 15a and n ⁺-type semiconductor region 15 b will be explained in detaillater, the rate of writing of data in each memory cell mainly can beenhanced.

The p-type semiconductor regions 15 are electrically coupled to thep-type well HPW2. The p-type semiconductor regions 15 and the p-typewell HPW2 are portions for forming an electrode for the chargeinjection/discharge section CWE. The p-type semiconductor region 15 iselectrically coupled to its corresponding conductor part 7 c lying in acontact hole CT defined in the insulating layer 6, through the silicidelayer 5 a formed in part of the surface layer of the correspondingp⁺-type semiconductor region 15 b. The conductor part 7 c iselectrically coupled to its corresponding data write/erase bit line WBL.

Capacitance sections C corresponding to plural bits are disposed in thep-type well HPW1. That is, each capacitance section C is formed in aposition (first position) where the first part of the floating gateelectrode FG planarly overlaps with the p-type well HPW1. Thecapacitance section C has a control gate electrode CGW, a capacitiveelectrode (first electrode) FGC2, a capacitive insulating film (firstinsulating film) 10 c and p-type semiconductor regions 17.

The control gate electrode CGW is formed by the p-type well HPW1 portionto which the floating gate electrode FG is opposed. The capacitiveelectrode FGC2 is formed by the first part of the floating gateelectrode FG opposite to the control gate electrode CGW. The length ofthe capacitive electrode FGC2 as viewed in the second direction X isformed so as to be longer than the lengths of the capacitive electrodeFGC1 of the data write/erase charge injection/discharge section CWE andthe gate electrode FGR of the data read MIS•FETQR as viewed in thesecond direction X. Thus, since the plan area of the capacitiveelectrode FGC2 can be ensured on a large scale, a coupling ratio can beenhanced and the efficiency of supply of a voltage from the control gateelectrode CGW can be increased.

The capacitive insulating film 10 c comprises, for example, siliconoxide and is formed between the control gate electrode CGW and thecapacitive electrode FGC2. The capacitive insulating film 10 c issimultaneously formed by a thermal oxidation process used upon formingthe gate insulating films 10 b and 10 e and the capacitive insulatingfilm 10 d. The thickness of the capacitive insulating film 10 c is 13.5nm or so, for example. The gate insulating films 10 b and 10 e and thecapacitive insulating films 10 c and 10 d are formed by the same processstep as one for a gate insulating film for each high breakdown MISFET,of high breakdown MISFETs each having a relatively thick gate insulatingfilm and low breakdown MISFETs each having a relatively thin gateinsulating film in the main circuit. Thus, the reliability of the flashmemory can be enhanced.

The p-type semiconductor regions 17 are formed in positions where theyinterpose the capacitive electrode FGC2 therebetween within the p-typewell HPW1. The semiconductor regions 17 respectively have p⁻-typesemiconductor regions 17 a on the channel side and p⁺-type semiconductorregions 17 b respectively coupled thereto. An impurity of the sameconduction type like, for, example, boron (B) or the like is containedin the p⁻-type semiconductor regions 17 a and p ⁺-type semiconductorregions 17 b. However, the impurity concentration of the p⁺-typesemiconductor region 17 b is set so as to be higher than that of thep⁻-type semiconductor region 17 a.

The semiconductor regions 17 on both sides of the capacitive electrodeFGC2 are both configured as a p type. However, it is also possible toconfigure one thereof as a p-type semiconductor region 17 and configurethe other (one side) thereof as an n-type semiconductor region 17. Inthis case, the semiconductor region 17 a of the other n-typesemiconductor region 17 is configured as an n⁻-type, and thesemiconductor region 17 b thereof is configured as an n⁺-type (higherthan n⁻-type in impurity concentration). Each semiconductor region canbe formed by causing the n⁻-type semiconductor region 17 a and n ⁺-typesemiconductor region 17 b to contain an impurity like arsenic (As) orphosphor (P). While the effect of providing each capacitance section Cwith the n⁻-type semiconductor region 17 a and n ⁺-type semiconductorregion 17 b will be explained in detail later, the rate of erasing ofdata in each memory cell mainly can be enhanced.

The p-type semiconductor regions 17 are electrically coupled to thep-type well HPW1. The p-type semiconductor regions 17 and the p-typewell HPW1 are portions for forming a control gate electrode CGW for thecapacitance section C. The p-type semiconductor region 17 iselectrically coupled to its corresponding conductor part 7 e lying in acontact hole CT defined in the insulating layer 6, through the silicidelayer 5 a formed in the surface layer of the corresponding p⁺-typesemiconductor region 17 b. The conductor part 7 e is electricallycoupled to its corresponding control gate wiring CG.

Meanwhile, the memory cells MC1 employed in the first embodiment aredifferent from the memory cells MC0 shown in FIGS. 1 and 2 in terms ofthe layout of the data read MIS•FETQR, capacitance sections C and datawrite/erase charge injection/discharge sections CWE.

In the memory cells MC1 employed in the first embodiment, the data readMIS•FETQR, the capacitance sections C and the data write/erase chargeinjection/discharge sections CWE are disposed in order from top tobottom as viewed in FIGS. 3 and 4. That is, each of the capacitancesections C is disposed between the data read MIS•FETQR and the chargeinjection/discharge section CWE.

In the first embodiment, the first part of the floating gate electrodeFG is provided between the second and third parts thereof as describedabove, and the second part having the gate electrode FGR of the dataread MIS•FETQR and the third part having the capacitive electrode FGC1of the data write/erase charge injection/discharge section CWE areseparated from each other.

Therefore, in the first embodiment, the length in the second directionX, of the second part of the floating gate electrode FG and the lengthin the second direction X, of the third part thereof can respectively beadjusted separately. Thus, the electrical characteristics of the flashmemory can be enhanced.

The present embodiment shows as an example, the case in which the lengthin the second direction X, of the second part (gate electrode FGR) ofthe floating gate electrode FG and the length in the second direction X,of the third part (capacitive electrode FGC1) thereof are equal to eachother. However, the length in the second direction X, of the third part(capacitive electrode FGC1) of the floating gate electrode FG may be setshorter than the length in the second direction X, of the second part(gate electrode FGR) of the floating gate electrode FG (thisconfiguration will be explained in the paragraph of another embodiment).The length in the second direction X, of the second part (gate electrodeFGR) of the floating gate electrode FG may be set shorter than thelength in the second direction X, of the third part (capacitiveelectrode FGC1) of the floating gate electrode FG (this configurationwill be explained in the paragraph of a further embodiment).

In the first embodiment, the length in the first direction Y, of thesecond part of the floating gate electrode FG and the length in thefirst direction Y, of the third part can respectively be adjusted in aseparate manner. Thus, the electrical characteristics of the flashmemory can be improved.

The present embodiment illustrates, as an example, the case in which thelength in the first direction Y, the third part of the floating gateelectrode FG is shorter than the length in the first direction Y, of thesecond part thereof. However, the length in the first direction Y, ofthe third part of the floating gate electrode FG may be set longer thanthe length in the first direction Y, of the second part. Alternatively,the length in the first direction Y, of the third part of the floatinggate electrode FG and the length in the first direction Y, of the secondpart may be set equal to each other.

In the first embodiment, the length from the capacitive electrode FGC2in the floating gate electrode FG to the data read MIS•FETQR can beshortened by a portion corresponding to the charge injection/dischargesection CWE non-interposed therebetween as compared with each of thememory cells MC0 shown in FIGS. 1 and 2. Thus, the electricalcharacteristics of the data read MIS•FETQR can be enhanced.

In the first embodiment, the positions in the second direction X, of thesecond part (gate electrode FGR) and the third part (capacitiveelectrode FGC1) can respectively be adjusted in a discrete manner byseparating the second and third parts of the floating gate electrode FGfrom each other as described above.

In the first embodiment, the second part (gate electrode FGR) of thefloating gate electrode FG and the third part (capacitive electrodeFGC1) thereof are disposed with being shifted in the direction movedaway from each other along the second direction X. Although the presentembodiment shows, as an example, the case in which the second and thirdparts are diagonally located, the present invention is not limited toit. One or both of the second and third parts may be located in portionsspaced away from the corners (opposite angles) of the first part(capacitive electrode FGC2).

Further, in the first embodiment, the memory cells MC1 adjacent to eachother are arranged in such a manner that the second parts (gateelectrodes FGR) of their floating gate electrodes FG approach each otherand the third parts (capacitive electrodes FGC1) thereof are moved awayfrom each other. Thus, the semiconductor regions 12 for the data readMIS•FETQR of the memory cells MC1 adjacent to each other can be broughtto the shared configuration as mentioned above while the semiconductorregions 15 and the p-type wells HPW2 in the charge injection/dischargesections CWE of the memory cells MC1 adjacent to each other remain inisolation respectively. Further, the semiconductor regions 17 for thecapacitance sections C of the memory cells MC1 adjacent to each othercan be brought to the shared configuration as described above. Thus,since the adjoining space in the second direction X defined between theadjacent memory cells MC1 can be closed up or reduced, the area of thememory cell array can be reduced. The storage capacity of each memorycan be increased.

The main circuit unit of the semiconductor device according to the firstembodiment will next be explained.

The LCD driver circuit corresponding to the main circuit unit of thefirst embodiment has a high breakdown section and a low breakdownsection. An operating voltage of each MIS•FET in the high breakdownsection is 25V or so, for example. As MIS•FETs in the low breakdownsection, may be mentioned, two types of one having an operating voltageof, for example, 6.0V, and one having an operating voltage of, forexample, 1.5V. The MIS•FET whose operating voltage is 1.5V is providedfor the purpose of operating at a velocity faster than the MIS•FET whoseoperating voltage is 6.0V. In the MIS•FET having the operating voltageof 1.5V, its gate insulating film is thinner than that for the MIS•FEThaving the operating voltage of 6.0V. The thickness of the gateinsulating film is formed in a range from about 1 nm to about 3 nm.

FIG. 9 is a cross-sectional view of a high breakdown section of a maincircuit unit employed in the semiconductor device according to the firstembodiment.

An n-type embedded well DNW and a p-type embedded well DPW are formed inthe high breakdown section of the substrate 1S of the semiconductorchip. A high breakdown n channel type MIS•FETQHN is formed in the p-typeembedded well DPW, and a p channel type MIS•FETQHP is formed in then-type embedded well DNW.

An impurity indicative of a p type like, for example, boron (B) or thelike is contained in the p-type embedded well. DPW. The n channel typeMIS•FETQHN formed in the p-type embedded well DPW has a gate electrodeGHN, a gate insulating film 10 f and n-type semiconductor regions 18 and18 for source/drain.

The gate electrode GHN comprises, for example, low-resistancepolycrystalline silicon, and a silicide layer 5 a is formed over itsupper surface. Sidewalls SW are formed over their corresponding sidesurfaces of the gate electrode GHN. The gate insulating film 10 fcomprises, for example, silicon oxide and is formed between the gateelectrode GHN and the substrate 1S. The thickness of the gate insulatingfilm 10 f is thicker than a gate insulating film of a low breakdownsection to be described later and ranges from about 50 nm to about 100nm, for example. Such a gate insulating film 10 f can also be formed bylaminating a film formed by thermal oxidation and a film deposited by aCVD method.

The n-type semiconductor regions 18 and 18 for source/drain areinternally wrapped in the p-type embedded well DPW. One of the n-typesemiconductor regions 18 and 18 has an n⁻-type semiconductor region 18 aon the channel side, and an n⁺-type semiconductor region 18 b coupledthereto. The other thereof has an n-type semiconductor region NV on thechannel side, and an n⁺-type semiconductor region 18 b coupled thereto.On the other n-type semiconductor region 18 side, an isolation part TIis provided between one end of the gate electrode GHN and the n⁺-typesemiconductor region 18 b. The n-type semiconductor region NV is coupledto the n⁺-type semiconductor region 18 b so as to straddle the isolationpart TI.

An impurity of the same conduction type like, for example, phosphor (P)or arsenic (As) or the like is contained in the semiconductor regions 18a, 18 b and NV. However, the impurity concentrations of thesemiconductor regions 18 a and 18 b are set so as to become higher thanthe impurity concentration of the n-type semiconductor region NV. Thesemiconductor regions 18 and 18 for source/drain are electricallycoupled to their corresponding conductor parts 7 lying in contact holesCT defined in the insulating layer 6, through silicide layers 5 a eachformed in part of a surface layer of the n⁺-type semiconductor region 18b.

The p channel type MIS•FETQHP has a gate electrode GHP, gate insulatingfilm 10 f and p-type semiconductor regions 19 and 19 for source/drain.

The gate electrode GHP comprises, for example, low-resistancepolycrystalline silicon and a silicide layer 5 a is formed over itsupper surface. Sidewalls SW are formed over their corresponding sidesurfaces of the gate electrode GHP. The gate insulating film 10 f forthe p channel type MIS•FETQHP is formed between the gate electrode GHPand the substrate 1S. The material and thickness of the gate insulatingfilm 10 f are the same as above.

The p-type semiconductor regions 19 and 19 for source/drain areinternally wrapped in the n-type embedded well DNW. One of the p-typesemiconductor regions 19 and 19 has a p⁻-type semiconductor region 19 aon the channel side, and a p⁺-type semiconductor region 19 b coupledthereto. The other thereof has a p-type semiconductor region PV on thechannel side, and a p⁺-type semiconductor region 19 b coupled thereto.On the other p-type semiconductor region 19 side, an isolation part TIis provided between one end of the gate electrode GHP and the p⁺-typesemiconductor region 19 b. The p-type semiconductor region PV is coupledto the p⁺-type semiconductor region 19 b so as to straddle the isolationpart TI.

An impurity of the same conduction type like, for example, boron (B) orthe like is contained in the semiconductor regions 19 a, 19 b and PV.However, the impurity concentrations of the semiconductor regions 19 a.and 19 b are set so as to become higher than the impurity concentrationof the p-type semiconductor region PV. The semiconductor regions 19 and19 for source/drain are electrically coupled to their correspondingconductor parts 7 lying in contact holes CT defined in the insulatinglayer 6, through silicide layers 5 a each formed in part of a surfacelayer of the p⁺-type semiconductor region 19 b.

Next, FIG. 10 shows a cross-sectional view of a low breakdown section ofthe main circuit unit employed in the semiconductor device illustrativeof the first embodiment of the present invention.

A p-type well PW and an n-type well NW are formed in the low breakdownsection of the substrate 1S in the semiconductor chip. An impurityindicative of a p type like, for example, boron (B) or the like iscontained in the p-type well PW. An impurity indicative of an n typelike, for example, phosphor (P) or arsenic (As) or the like is containedin the n-type well NW. The p-type well PW and the n-type well NW areinternally wrapped in an n-type embedded well DNW.

A low breakdown n channel type MIS•FETQLN1 is formed in a p-type wellHPW4 lying in a 6V system device forming area. The n channel typeMIS•FETQLN1 is of a device whose operating voltage is 6V and has a gateelectrode GLN1, a gate insulating film 10 g and a pair of n-typesemiconductor regions 20 and 20 for source/drain.

The gate electrode GLN1 comprises, for example, low-resistancepolycrystalline silicon, and a silicide layer 5 a is formed over itsupper surface. Sidewalls SW are formed over their corresponding sidesurfaces of the gate electrode GLN1. The gate insulating film 10 gcomprises, for example, silicon oxide and is formed between the gateelectrode GLN1 and the substrate 1S. The thickness of the gateinsulating film 10 g is thinner than the gate insulating film for theMIS•FET of the high breakdown section and is 13.5 nm or so, for example.

The n-type semiconductor regions 20 and 20 for source/drain areinternally wrapped in the p-type well HPW4. Each of the n-typesemiconductor regions 20 and 20 has an n⁻-type semiconductor region 20 aon the channel side, and an n⁺-type semiconductor region 20 b coupledthereto. An impurity of the same conduction type like, for example,phosphor (P) or arsenic (As) or the like is contained in thesemiconductor regions 20 a and 20 b. However, the impurity concentrationof the n⁺-type semiconductor region 20 b is set so as to be higher thanthat of the n⁻-type semiconductor region 20 a.

The semiconductor regions 20 and 20 for source/drain are electricallycoupled to their corresponding conductor parts 7 lying in contact holesCT defined in the insulating layer 6, through silicide layers 5 a eachformed in part of a surface layer of the n⁺-type semiconductor region 20b.

A low breakdown p channel type MIS•FETQLP1 is formed in an n-type wellHNW lying in the 6V system device forming area. The p channel typeMIS•FETQLP1 is of a device whose operating voltage is 6V and has a gateelectrode GLP1, a gate insulating film 10 g and a pair of p-typesemiconductor regions 20 and 20 for source/drain.

The gate electrode GLP1 comprises, for example, low-resistancepolycrystalline silicon and a silicide layer 5 a is formed over itsupper surface. Sidewalls SW are formed over their corresponding sidesurfaces of the gate electrode GLP1. The gate insulating film 10 gcomprises, for example, silicon oxide and is formed between the gateelectrode GLP1 and the substrate 1S. The material and thickness of thegate insulating film 10 g are the same as above.

The p-type semiconductor regions 21 and 21 for source/drain areinternally wrapped in an n-type well HNW. Each of the p-typesemiconductor regions 21 and 21 has a p⁻-type semiconductor region 21 aon the channel side, and a p⁺-type semiconductor region 21 b coupledthereto. An impurity of the same conduction type like, for example,boron (B) or the like is contained in the semiconductor regions 21 a, 21b. However, the impurity concentration of the p⁺-type semiconductorregion 21 b is set so as to become higher than the impurityconcentration of the p⁻-type semiconductor region 21 a.

The semiconductor regions 21 and 21 for source/drain are electricallycoupled to their corresponding conductor parts 7 lying in contact holesCT defined in the insulating layer 6, through silicide layers 5 a eachformed in part of a surface layer of the p⁺-type semiconductor region 21b.

A low breakdown n channel type MIS•FETQLN2 is formed in a p-type well PWlying in a 1.5V system device forming area. The n channel typeMIS•FETQLN2 is of a device whose operating voltage is 1.5V and has agate electrode GLN2, a gate insulating film 10 h and a pair of n-typesemiconductor regions 22 and 22 for source/drain.

The gate electrode GLN2 comprises, for example, low-resistancepolycrystalline silicon and a silicide layer 5 a is formed over itsupper surface. The lateral or transverse length (or gate length) of thegate electrode GLN2 is smaller than the transverse length (or gatelength) of the gate electrode GLN1 of the low breakdown n channel typeMIS•FETQLN1 (whose operating voltage is 6V). Sidewalls SW are formedeven over their corresponding side surfaces of such a gate electrodeGLN2.

The gate insulating film 10 h comprises, for example, silicon oxide andis formed between the gate electrode GLN2 and the substrate 1S. Thethickness of the gate insulating film 10 h is thinner than the gateinsulating film for the MIS•FET of the low breakdown section and is 3.7nm or so, for example.

The n-type semiconductor regions 22 and 22 for source/drain areinternally wrapped in the p-type well PW. Each of the n-typesemiconductor regions 22 and 22 has an n⁻-type semiconductor region 22 aon the channel side, and an n⁺-type semiconductor region 22 b coupledthereto. An impurity of the same conduction type like, for example,phosphor (P) or arsenic (As) or the like is contained in thesemiconductor regions 22 a and 22 b. However, the impurity concentrationof the n⁺-type semiconductor region 22 b is set so as to be higher thanthat of the n⁻-type semiconductor region 22 a.

As the configurations of the pair of n-type semiconductor regions 22 forsource/drain, p-type semiconductor regions (p-type hollow regions orp-type punchthrough stopper regions) are formed near the ends of then⁻-type semiconductor regions 22 a. Thus, a short channel effect of then channel type MIS•FETQLN2 smaller than the n channel type MIS•FETQLN1can be suppressed or prevented.

The semiconductor regions 22 and 22 for source/drain are electricallycoupled to their corresponding conductor parts 7 lying in contact holesCT defined in the insulating layer 6, through silicide layers 5 a eachformed in part of a surface layer of the n⁺-type semiconductor region 22b.

A low breakdown p channel type MIS•FETQLP2 is formed in the n-type wellPW lying in the 1.5V system device forming area. The p channel typeMIS•FETQLP2 is of a device whose operating voltage is 1.5V and has agate electrode GLP2, a gate insulating film 10 h and a pair of p-typesemiconductor regions 23 and 23 for source/drain.

The gate electrode GLP2 comprises, for example, low-resistancepolycrystalline silicon and a silicide layer 5 a is formed over itsupper surface. The lateral or transverse length (or gate length) of thegate electrode GLP2 is smaller than the transverse length (or gatelength) of the gate electrode GLP1 of the low breakdown p channel typeMIS•FETQLP1 (whose operating voltage is 6V). Sidewalls SW are formedeven over their corresponding side surfaces of such a gate electrodeGLP2. The gate insulating film 10 h of the p channel type MIS•FETQLP2 isformed between the gate electrode GLP2 and the substrate 1S. Thematerial and thickness of the gate insulating film 10 h are the same asabove.

The p-type semiconductor regions 23 and 23 for source/drain areinternally wrapped in the n-type well NW. Each of the p-typesemiconductor regions 23 and 23 has an p⁻-type semiconductor region 23 aon the channel side, and an p⁺-type semiconductor region 23 b coupledthereto. An impurity of the same conduction type like, for example,boron (B) or the like is contained in the semiconductor regions 23 a and23 b. However, the impurity concentration of the p⁺-type semiconductorregion 23 b is set so as to be higher than that of the p⁻-typesemiconductor region 23 a.

As the configurations of the pair of p-type semiconductor regions 23 forsource/drain, p-type semiconductor regions (p-type hollow regions orp-type punchthrough stopper regions) are formed near the ends of then⁻-type semiconductor regions 22 a. Thus, a short channel effect of thep channel type MIS•FETQLP2 smaller than the p channel type MIS•FETQLP1can be suppressed or prevented.

The semiconductor regions 23 and 23 for source/drain are electricallycoupled to their corresponding conductor parts 7 lying in contact holesCT defined in the insulating layer 6, through silicide layers 5 a eachformed in part of a surface layer of the p⁺-type semiconductor region 23b.

Next, FIG. 11 shows a fragmentary circuit diagram of the flash memoryfor the semiconductor device according to the first embodiment.

The flash memory has the memory cell array MR and a peripheral circuitarea or region PR. A plurality of data write/erase bit lines WBL (WBL0,WBL1, . . . ) extending in a first direction Y, and data read bit linesRBL (RBL0, RBL2, . . . ) are arranged in the memory cell array MR alonga second direction X. Further, a plurality of control gate wirings (wordlines) CG (CG0, CG1, . . . ) extending along the second direction Xorthogonal to the bit lines WBL and RBL, a plurality of source lines SLand a plurality of selection lines GS are arranged in the memory cellarray MR along the first direction Y.

The respective data write/erase bit lines WBL are electrically coupledor coupled to their corresponding data (0/1) input inverter circuits INVarranged in the peripheral circuit area PR. The respective data read bitlines RBL are electrically coupled to their corresponding senseamplifier circuits SA arranged in the peripheral circuit area PR. Eachof the sense amplifier circuits SA is configured as a current mirrortype, for example. Memory cells MC1 each corresponding to one bit arerespectively electrically coupled to the neighborhoods of lattice-likeintersecting points of the bit lines WBL and RBL and the control gatewirings CG, the source lines SL and the selection lines GS. A case inwhich one bit is constituted of one memory cell MC1, is illustrated byway of example here.

The memory cell MC1 has a data write/erase capacitance section (chargeinjection/discharge section) CWE, a data read MIS•FETQR, a capacitancesection C and a selection MIS•FETQS. One electrode of the datawrite/erase charge injection/discharge section CWE for each bit iselectrically coupled to its corresponding data write/erase bit line WBL.The other electrode (floating gate electrode FG) of the data write/erasecharge injection/discharge section CWE is electrically coupled to itscorresponding gate electrode (floating gate electrode FG) of each dataread MIS•FETQR and coupled to one electrode (floating gate electrode FG)of the capacitance section C. The other electrode (control gateelectrode CGW) of the capacitance section C is electrically coupled toits corresponding control gate wiring CG. On the other hand, the drainof the data read MIS•FETQR of one memory cell MC corresponding to eachbit is electrically coupled to its corresponding data read bit line RBLvia the selection MIS•FETQS, and the source thereof is electricallycoupled to its corresponding source line SL. The gate electrode of theselection MIS•FETQS is electrically coupled to the selection line GS.

Examples illustrative of data write operations of such a flash memorywill next be explained with reference to FIGS. 12 through 15.

FIG. 12 shows voltages applied to respective parts at a data writeoperation of the flash memory shown in FIG. 11. A broken line S1indicates a memory cell MC1 (hereinafter called selection memory cellMC1 s) targeted for data writing. Incidentally, the injection ofelectrons in the floating gate electrode is defined as data writing. Inreverse, the extraction or ejection of electrons from the floating gateelectrode can also be defined as data writing.

Upon the writing of data, a positive control voltage of, for example, 9Vor so is applied to a control gate wiring CG0 (CG) to which the otherelectrode of the capacitance section C in the selection memory cell MC1s is electrically coupled. A voltage of, for example, 0V is applied to acontrol gate wiring CG1 (CG) other that it. A negative voltage of, forexample, −9V or so is applied to the data write/erase bit line WBL0(WBL) to which one electrode of the data write/erase chargeinjection/discharge section CWE of the selection memory cell MC1 s iselectrically coupled. A voltage of, for example, 0V is applied to thedata write/erase bit line WBL1 (WBL) other than it. For example, 0V isapplied to the corresponding selection line GS, source line SL and dataread bit line RBL. Thus, electrons are injected into the floating gateelectrode of the data write/erase charge injection/discharge section CWEof the selection memory cell MC1 s by an FN tunnel current at a channelentire surface to write data.

Next, FIG. 13 shows voltages applied to the respective parts at a databatch-erase operation of the flash memory shown in FIG. 11. A brokenline S2 indicates a plurality of memory cells MC1 (hereinafter calledselection memory cells MC1 se) targeted for data batch-erasure.Incidentally, the extraction or ejection of electrons from the floatinggate electrode is defined as data erasure. In reverse, the injection ofelectrons into the floating gate electrode can also be defined as dataerasure.

Upon data batch-erasing, a negative control voltage of, for example, −9Vor so is applied to control gate wirings CG0 and CG1 (CG) to which theother electrodes of the capacitance sections C in the selection memorycells MC1 se are electrically coupled. A negative voltage of, forexample, −9V or so is applied to the data write/erase bit lines WBL0 andWBL1 (WBL) to which one electrodes of the data write/erase chargeinjection/discharge sections CWE of the selection memory cells MC1 seare electrically coupled. For example, 0V is applied to thecorresponding selection lines GS, source lines SL and data read bitlines RBL. Thus, electrons stored in the floating gate electrodes of thedata write/erase charge injection/discharge sections CWE in theselection memory cells MC1 se that perform the data batch-erasing aredischarged by an FN tunnel current at the entire surface of a channel,thereby to batch-erase data of the selection memory cells MC1 se.

Next, FIG. 14 shows voltages applied to the respective parts at adata-bit unit erase operation of the flash memory shown in FIG. 11. Abroken line S3 indicates a memory cell MC (called selection memory cellMC1 se) targeted for data erasure.

Upon data-bit unit erasure, a negative control voltage of, for example,−9V or so is applied to a control gate wiring CG0 (CG) to which theother electrode of the capacitance section C in the selection memorycell MC1 se is coupled. A voltage of, for example, 0V is applied to acontrol gate wiring CG1 (CG) other that it. A positive voltage of, forexample, 9V or so is applied to the data write/erase bit line WBL0 (WBL)to which one electrode of the data write/erase chargeinjection/discharge section CWE of the selection memory cell MC1 se iselectrically coupled. A voltage of, for example, 0V is applied to thedata write/erase bit line WBL1 (WBL) other than it. For example, 0V isapplied to the corresponding selection line GS, source line SL and dataread bit line RBL. Thus, electrons stored in the floating gate electrodeof the data write/erase charge injection/discharge section CWE of theselection memory cell MC1 se targeted for data erasure are discharged byan FN tunnel current at a channel entire surface, thereby erasing dataof the selection memory cell MC1 se targeted for data erasure.

Next, FIG. 15 shows voltages applied to the respective parts at a dataread operation of the flash memory shown in FIG. 11. A broken line S4indicates memory cells MC1 (hereinafter called selection memory cellsMC1 r) targeted for data reading.

Upon data reading, a control voltage of, for example, 3V or so isapplied to its corresponding control gate wiring CG0 (CG) to which theother electrodes of the capacitance sections C of the selection memorycells MC1 r are coupled. A voltage of, for example, 0V is applied to thecorresponding control gate wiring CG1 (CG) other than above. A voltageof, for example, 0V or so is applied to the data write/erase bit linesWBL0 and WBL1 (WBL) to which one electrodes of the data write/erasecharge injection/discharge sections CWE of the selection memory cellsMC1 r are electrically coupled. A voltage of, for example, 3V or so isapplied to the corresponding selection line GS to which the gateelectrodes of the selection MIS•FETQS of the selection memory cells MC1r are electrically coupled. A voltage of, for example, 1V or so isapplied to the corresponding data read bit line RBL. Further, forexample, 0V is applied to the corresponding source line SL. Thus,whether data stored in the corresponding selection memory cell MC1 r iseither 0 or 1 is read according to whether a drain current flows througha channel for each of data read MIS•FETQR of the selection memory cellsMC1 r targeted for data reading, under the condition that each of thedata read MIS•FETQR of the selection memory cells MC1 r targeted fordata reading is on.

The manner of the memory cell MC1 at the operation of the flash memoryaccording to the first embodiment will next be explained using FIGS. 16through 18. Incidentally, the numerics inside the parentheses indicateapplied voltages respectively.

FIG. 16 shows a cross-sectional view taken along line Y1-Y1 of FIG. 3 atthe data write operation of the flash memory according to the firstembodiment.

Here, a voltage of, for example, 9V or so is applied to the n-type wellHNW and the n-type embedded well DNW through the conductor parts 7 b toelectrically isolate the substrate 1S and the p-type wells HPW1 throughHPW3. A positive control voltage of, for example, 9V or so is appliedfrom the control gate wiring CG to the control gate electrode CGW of thecapacitance section C through each conductor part 7 e. A negativevoltage of, for example, −9V or so is applied from the data write/erasebit line WBL to one electrode (p-type semiconductor region 15 and p-typewell HPW2) of the charge injection/discharge section CWE through thecorresponding conductor part 7 c.

For example, 0V is applied to the p-type well HPW3 through itscorresponding conductor part 7 a. For example, 0V is applied from theselection line GS to the gate electrode FGS of the selection MIS•FETQSthrough the corresponding conductor part 7 f. For example, 0V is appliedfrom the source line SL to one n-type semiconductor region 12 of thedata read MIS•FETQR through the corresponding conductor part 7 d. Forexample, 0V is applied from the data read bit line RBL to one n-typesemiconductor region 12 of the selection MIS•FETQS through thecorresponding conductor part 7 g.

Thus, electrons e of the p-type well HPW2 are injected into thecorresponding capacitive electrode FGC1 (floating gate electrode FG)through the capacitive insulating film 10 d by an FN tunnel current at achannel entire surface in the data write/erase chargeinjection/discharge section CWE of the selected memory cell MC1 therebyto write data therein.

The effect of forming one of the semiconductor regions 15 of the chargeinjection/discharge section CWE by the n⁻-type semiconductor region 15 aand the n⁺-type semiconductor region 15 b as described above will beexplained here. When the n-type semiconductor regions 15 exist, theformation of the inversion layer extending from each n-typesemiconductor region 15 is promoted. The electrons are minority carriersin the p-type semiconductor, whereas the electrons are majority carriersin the n-type semiconductor. Therefore, the electrons to be injected canbe easily supplied to the inversion layer placed directly below thecapacitive electrode FGC1. As a result, since effective couplingcapacitance can be increased, the potential of the capacitive electrodeFGC1 can be controlled efficiently. It is thus possible to enhance adata write rate. A variation in the data write rate can also be reduced.

Next, FIG. 17 shows a cross-sectional view taken along line Y1-Y1 ofFIG. 3 at a data erase operation of the flash memory according to thefirst embodiment.

Here, a voltage of, for example, 9V or so is applied to the n-type wellHNW and the n-type embedded well DNW through the conductor parts 7 b toelectrically isolate the substrate 1S and the p-type wells HPW1 throughHPW3. A negative control voltage of, for example, −9V or so is appliedfrom the control gate wiring CG to the control gate electrode CGW of thecapacitance section C through each conductor part 7 e. A positivevoltage of, for example, 9V or so is applied from the data write/erasebit line WBL to one electrode (p-type semiconductor region 15 and p-typewell HPW2) of the charge injection/discharge section CWE through thecorresponding conductor part 7 c.

For example, 0V is applied to the p-type well HPW3 through itscorresponding conductor part 7 a. For example, 0V is applied from theselection line GS to the gate electrode FGS of the selection MIS•FETQSthrough the corresponding conductor part 7 f. For example, 0V is appliedfrom the source line SL to one n-type semiconductor region 12 of thedata read MIS•FETQR through the corresponding conductor part 7 d. Forexample, 0V is applied from the data read bit line RBL to one n-typesemiconductor region 12 of the selection MIS•FETQS through thecorresponding conductor part 7 g.

Thus, the electrons e stored in the capacitive electrode FGC1 (floatinggate electrode FG) are discharged to the p-type well HPW2 through thecapacitive insulating film 10 d by an FN tunnel current at the channelentire surface in the data write/erase charge injection/dischargesection CWE of the selected memory cell MC1 thereby to erase data.

The effect of forming one of the semiconductor regions 17 of thecapacitance section C by the n⁻-type semiconductor region 17 a and then⁺-type semiconductor region 17 b as described above will be explainedhere. Upon data erasure, the electrons can smoothly be supplied todirectly below the capacitive insulating film 10 c by addition of then-type semiconductor regions 17. Therefore, the p-type well HPW1 canpromptly be fixed to −9V because the inversion layer can quickly beformed. As a result, since effective coupling capacitance can beincreased, the potential of the capacitive electrode FGC2 can becontrolled efficiently. It is thus possible to enhance a data eraserate. A variation in the data erase rate can also be reduced.

Next, FIG. 18 shows a cross-sectional view taken along line Y1-Y1 ofFIG. 3 at a data read operation of the flash memory according to thefirst embodiment.

Here, a voltage of, for example, 3V or so is applied to the n-type wellHNW and the n-type embedded well DNW through each conductor part 7 b toelectrically isolate the substrate 1S and the p-type wells HPW1 throughHPW3.

A positive control voltage of, for example, 3V or so is applied from thecontrol gate wirings CG to the control gate electrode CGW of thecapacitance section C through the conductor parts 7 e. Thus, thepositive voltage is applied to the gate electrode FGR of the data readMIS•FETQR.

For example, 0V is applied to the p-type well HPW3 through itscorresponding conductor part 7 a. For example, 3V is applied from theselection line GS to the gate electrode FGS of the selection MIS•FETQSthrough the corresponding conductor part 7 f. For example, 0V is appliedfrom the source line SL to one n-type semiconductor region 12 of thedata read MIS•FETQR through the corresponding conductor part 7 d. Forexample, 1V is applied from the data read bit line RBL to one n-typesemiconductor region 12 of the selection MIS•FETQS through thecorresponding conductor part 7 g.

For example, a voltage of, for example, 0V is applied from the datawrite/erase bit line WBL to one electrode (p-type semiconductor region15 and p-type well HPW2) of the charge injection/discharge section CWEthrough the corresponding conductor part 7 c.

Thus, whether data stored in the corresponding selection memory cell MC1is either 0 or 1 is read according to whether a drain current flowsthrough a channel for the data read MIS•FETQR of the selected memorycell MC1, under the condition that the data read MIS•FETQR of theselected memory cell MC1 is on.

According to the first embodiment referred to above, the data rewritearea (charge injection/discharge section CWE), the data read area (dataread MIS•FETQR) and the capacitance coupling area (capacitance sectionC) are formed in their corresponding separate p-type wells HPW1 throughHPW3 and respectively separated by the n-type well HNW and the n-typeembedded well DNW. Data rewriting is performed by each capacitiveelement.

Thus, since there is no need to provide the cut-off transistor in thedata rewrite area of the flash memory, miniaturization of thesemiconductor device can be promoted.

Since the data rewriting element is formed of the capacitive element,and the p-type semiconductor regions 15 and the p-type well HPW2 becomeidentical in potential upon data rewriting by the FN tunnel current atthe entire surface of the channel, the problem of a junction breakdownvoltage no longer occurs. Therefore, it is possible to suppress orprevent deterioration of the memory cell MC1 of the flash memory andenhance the reliability of operation of the flash memory.

Since the scale of each peripheral circuit of the flash memory can beless reduced because no timing design is required, miniaturization ofthe semiconductor device can be promoted. Since the data rewriting canbe done by the FN tunnel current at the channel entire surface, which issuitable for rewriting or reloading of a single power supply that issmallest in current consumption and held at a low voltage, singlepowering by an internal step-up circuit is easy.

Further, since the channel FN tunnel current free of the occurrence ofholes is used upon the data writing/erasure, the number of rewritings ofdata can be enhanced.

The data rewrite area (charge injection/discharge section CWE) and thedata read area (data read MIS•FETQR) are formed within theircorresponding separate p-type wells HPW2 and HPW3, thereby making itpossible to stabilize data rewriting. It is therefore possible toenhance the reliability of operation of the flash memory.

Second Preferred Embodiment

A second embodiment is different from the first embodiment in thefollowing configurations in particular.

The first is that the configurations of a pair of semiconductor regionsfor source/drain, of a data read MIS•FET of each memory cell areidentical to the configurations (including the p-type hollow regions) ofthe pair of semiconductor regions for source/drain, of the n channeltype MIS•FET of the low breakdown section (1.5V device) in the maincircuit.

The second is that the gate length of each data write/erase chargeinjection/discharge section of the memory cell is made short, and partof a p-type semiconductor region of the charge injection/dischargesection is caused to extend (diffuse into) to a surface layer of asubstrate placed directly below a capacitive electrode.

The third is that p-type wells of the charge injection/dischargesections adjacent to each other are separated by n⁺-type semiconductorregions (each corresponding to an n⁺-type diffusion layer) higher thanthe n-type wells in impurity concentration.

A specific example of a configuration of a flash memory for asemiconductor device according to the second embodiment will beexplained below with reference to FIGS. 19 through 24. FIG. 19 is a planview of the flash memory for the semiconductor device illustrative ofthe second embodiment, FIG. 20 is a fragmentary enlarged plan view ofthe flash memory shown in FIG. 19, FIG. 21 is a cross-sectional viewtaken along line Y2-Y2 of FIG. 19, FIG. 22 is a cross-sectional viewtaken along line X1-X1 of FIG. 20, FIG. 23 is a cross-sectional viewtaken along line X2-X2 of FIG. 20, and FIG. 24 is a cross-sectional viewtaken along line X3-X3 of FIG. 20, respectively. Incidentally, althoughFIGS. 19 and 20 are plan views, parts thereof are hatched to make iteasy to see the drawings.

In the second embodiment, as described above, the pair of semiconductorregions for source/drain, of the data read MIS•FETQR of each memory cellMC1 is made identical in configuration to the pair of semiconductorregions for source/drain, of the n channel type MIS•FETQLN2 of the lowbreakdown section (1.5V device) in the main circuit.

In this case, the pair of semiconductor regions for source/drain, ofeach data read MIS•FETQR has n-type semiconductor regions 12 eachconstituted of an n⁻-type semiconductor region 12 a and an n⁺-typesemiconductor region 12 b as described in the first embodiment, andfurther includes p-type semiconductor regions (p-type hollow regions orp-type punchthrough stopper regions) formed near the ends on the channelside, of the n⁻-type semiconductor regions 12 a.

Thus, since a short channel effect at each data read MIS•FETQR can besuppressed or prevented, the data read MIS•FETQR can be miniaturized.Therefore, the area of a memory cell array MR can be scaled down becausethe size of the memory cell MC1 can be reduced. Further, the storagecapacity of the memory can be increased.

A pair of semiconductor regions for source/drain, of each selectionMIS•FETQS of the memory cell MC1 is identical in configuration to thepair of semiconductor regions for source/drain, of the n channel typeMIS•FETQLN2 of the low breakdown section (1.5V device) in the maincircuit.

In this case, the pair of semiconductor regions for source/drain, ofeach selection MIS•FETQS has n-type semiconductor regions 12 eachconstituted of an n⁻-type semiconductor region 12 a and an n⁺-typesemiconductor region 12 b as described in the first embodiment, andfurther includes p-type semiconductor regions (p-type hollow regions orp-type punchthrough stopper regions) formed near the ends on the channelside, of the n⁻-type semiconductor regions 12 a.

Thus, since a short channel effect at each selection MIS•FETQS can besuppressed or prevented, the selection MIS•FETQS can be miniaturized.Therefore, the area of the memory cell array MR can be scaled downbecause the size of the memory cell MC1 can be reduced. Further, thestorage capacity of the memory can be increased.

Since only a voltage of 0V or 1V is applied to the pairs ofsemiconductor regions for source/drain, of the data read MIS•FETQR andselection MIS•FETQS upon operation of the memory cell MC1, the data readMIS•FETQR and the selection MIS•FETQS can be formed by 1.5V-systemMIS•FETs.

However, the thickness of each of gate insulating films 10 b and 10 efor the data read MIS•FETQR and selection MIS•FETQS is identical to thatdescribed in the first embodiment and formed thicker than the gateinsulating film 10 h for the n channel type MIS•FETQLN2 of the lowbreakdown section (1.5V device) in the main circuit. This is because adifference in potential of 3V or more occurs between the gate insulatingfilms 10 b and 10 e upon the operation of the memory cell.

The length (gate length) in a second direction X, of a capacitiveelectrode FGC1 of a data write/erase charge injection/discharge sectionCWE of each memory cell MC1 is shorter than the length (gate length) inthe second direction X, of a gate electrode FGR of each data readMIS•FETQR. Parts (parts of p⁻-type semiconductor regions 15 a and 15 a)of a pair of p-type semiconductor regions 15 and 15 on both sides asviewed in the second direction X, of the capacitive electrode FGC1 ofthe charge injection/discharge section CWE are extended over a surfacelayer of a substrate 1S placed directly below the capacitive electrodeFGC1. A case in which the tips or leading end portions on the channelside, of the p⁻-type semiconductor regions 15 a and 15 a of the pair ofp-type semiconductor regions 15 and 15 intrude directly below thecapacitive electrode FGC1 and are held in contact with each other, isillustrated by way of example as shown in FIGS. 21 and 23 here.

When a negative voltage of, for example, −9V or so is applied to itscorresponding p-type well HPW2 of the charge injection/discharge sectionCWE upon data writing where the parts of the p-type semiconductorregions 15 of the charge injection/discharge section CWE are notextended over the surface layer of the substrate 1S directly below thecapacitive electrode FGC1 as described in the first embodiment, adepletion layer is formed in the surface layer of the substrate 1Sdirectly below the capacitive insulating film 10 d. As a result, thereare cases in which coupling capacitance is decreased and a data writerate is reduced, and a variation occurs in the data write rate.

On the other hand, when the parts of the p-type semiconductor regions 15are extended (diffused) directly below the capacitive electrode FGC1 asin the second embodiment, the concentration of a p-type impurity lyingin the surface layer of the substrate 1S directly below the capacitiveelectrode FGC1 can be made high. It is therefore possible to suppress orprevent the formation of the depletion layer in the surface layer of thesubstrate 1S directly below the capacitive electrode FGC1 upon datarewriting (write/erase). Thus, since effective coupling capacitance canbe increased, the potential of the capacitive electrode FGC1 (floatinggate electrode FG) can be controlled efficiently. It is thus possible toenhance a data write rate. A variation in the data write rate can alsobe reduced.

In the second embodiment, the p-type wells HPW2 of the chargeinjection/discharge sections CWE adjacent to each other along the seconddirection X are separated from each other by an n⁺-type semiconductorregion (n⁺-type diffusion layer) 25 formed between the p-type wells HPW2adjacent to each other within the memory cell array MR. The impurityconcentration of the n⁺-type semiconductor region 25 is higher than theimpurity concentration of each of the above n-type well HNW and n-typeembedded well DNW.

When the p-type wells HPW2 and HPW2 of the charge injection/dischargesections CWE adjacent to each other are separated from each other by then-type well HNW and the n-type embedded well DNW as in the firstembodiment, there is a limit to narrow the adjoining space or intervalbetween the p-type wells HPW2 and HPW2 from the viewpoint of inhibitionof the formation of a parasitic MOS•FET between the adjacent p-typewells HPW2 and HPW2, for example.

On the other hand, since the impurity concentration of the n⁺-typesemiconductor region 25 is higher than the impurity concentration ofeach of the n-type well HNW and the n-type embedded well DNW where thep-type wells HPW2 adjacent to each other along the second direction Xare separated by the n⁺-type semiconductor region (n⁺-type diffusionlayer) 25 as in the second embodiment, the formation of the parasiticMOS•FET can be suppressed or prevented even though the adjoining spacebetween the p-type wells HPW2 and HPW2 is made narrow. Thus, theadjoining space between the p-type wells HPW2 and HPW2 adjacent to eachother along the second direction X can be narrowed as compared withfirst embodiment. It is therefore possible to reduce the area of thememory cell array MR. Further, the storage capacity of the memory can beincreased.

The n⁺-type semiconductor region 25 is formed simultaneously uponformation of each device in the main circuit. Thus, the number ofprocess steps for manufacturing the semiconductor device does notincrease even supposing that the n⁺-type semiconductor region 25 wasformed. It is thus possible to prevent the time required to manufacturethe semiconductor device from increasing and prevent an increase in thecost of semiconductor device.

One example of a method for manufacturing a semiconductor deviceaccording to the present embodiment will next be explained withreference to FIGS. 25 through 42. Incidentally, FIGS. 25 through 42respectively show fragmentary cross-sectional views illustrative of asubstrate 1S (corresponding to an approximately circular semiconductorthin board or plate called a wafer in this stage) during themanufacturing process of the semiconductor device according to thepresent embodiment. Here, a low breakdown section and a flash memory areshown and a high breakdown section is not illustrated. Selection MISsare also omitted.

As shown in FIGS. 25 and 26, a p-type substrate 1S (wafer) is firstprepared. The substrate 1S has a first main surface and a second mainsurface located on the sides opposite to each other along its thicknessdirection.

Subsequently, an n-type embedded well DNW is formed simultaneously inthe low breakdown section, a memory cell forming area of the flashmemory and the high breakdown section by a photolithography (hereinaftercalled simply lithography) process and an ion implanting process or thelike. The lithography process is a series of process steps for formingdesired resist patterns by application of a photoresist film(hereinafter called simply resist) film, exposure and development or thelike. In the ion implanting process, desired impurities are selectivelyintroduced into desired portions of the substrate 1S with the resistpatterns formed over the main surface of the substrate 1S through thelithography process as masks. The resist patterns shown here are definedas such patterns that impurity introducing regions are exposed andregions other than the same are covered.

Incidentally, a p-type embedded well DPW is formed by thephotolithography process and the ion implanting process or the like inthe high breakdown section prior to the impurity introducing step forforming the n-type embedded well DNW.

Thereafter, isolation trenches are formed in an isolation area of thefirst main surface of the substrate 1S. Afterwards, an insulating filmis embedded into the isolation trenches to form trench-type isolationparts TI. Thus, active regions are defined. The isolation parts TI maybe formed before the process steps for forming the p-type embedded wellDPW and n-type embedded well DNW.

Next, the n-type semiconductor region NV is formed in its correspondingn channel type MIS•FET forming region of the high breakdown section bythe lithography process and the ion implanting process or the like. Thep-type semiconductor region PV is formed in its corresponding p channeltype MIS•FET forming region of the high breakdown section by thelithography process and the ion implanting process or the like (see FIG.9). The impurity concentration of the n-type semiconductor region NV ishigher than that of the n-type embedded well DNW, and the impurityconcentration of the p-type semiconductor region PV is higher than thatof the p-type embedded well DPW.

Subsequently, as shown in FIGS. 27 and 28, an n-type well HNW is formedin a p channel type MIS•FET forming region of a 6V device forming areaof the low breakdown section and each isolation region of a memory cellforming area of the flash memory by the lithography process and the ionimplanting process or the like.

Subsequently, p-type wells HPW1 through HPW4 are simultaneously formedin an n channel type MIS•FET forming region of the 6V device formingarea of the low breakdown section and the memory cell forming area ofthe flash memory by the lithography process and the ion implantingprocess or the like.

Then, as shown in FIGS. 29 and 30, an n-type well NW is formed in a pchannel type MIS•FET forming region of a 1.5V device forming area of thelow breakdown section by the lithography process and the ion implantingprocess or the like.

Subsequently, a p-type well PW is formed in an n channel type MIS•FETforming region of the 1.5V device forming area of the low breakdownsection by the lithography process and the ion implanting process or thelike.

Thereafter, as shown in FIGS. 31 and 32, gate insulating films 10 b, 10g and 10 h and capacitive insulating films 10 c and 10 d are formed overthe first man surface of the substrate 1S by a thermal oxidation methodor the like. The gate insulating films 10 b and 10 g and the capacitiveinsulating films 10 c and 10 d are formed simultaneously. Theirthicknesses preferably range from 10 nm to 20 nm, for example and areset to 13.5 nm, for example.

On the other hand, the gate insulating films 10 h for the p channel typeMIS•FET forming region and the n channel type MIS•FET forming region inthe 1.5V device forming area are formed simultaneously. Theirthicknesses are thinner than those of the gate insulating films 10 b and10 g and the capacitive insulating films 10 c and 10 d and are 3.7 nm orso, for example.

Changing the thickness of each insulating film in this way is performedin the following manner, for example. An insulating film is formed bysubjecting the first main surface of the substrate 1S to a thermaloxidation process. Thereafter, a thin-film portion of the insulatingfilm is selectively removed. Subsequently, a thermal oxidation processcorresponding to a second time is effected on the first main surface ofthe substrate 1S. Thus, a thick insulating film is formed at athick-film portion and a thin insulating film is formed at the thin-filmportion. In place of the thermal oxidation process corresponding to thesecond time, the insulating film may be deposited using a CVD (ChemicalVapor Deposition) method or the like.

Thereafter, a conductor film constituted of, for example, low-resistancepolycrystalline silicon is deposited over the first main surface of thesubstrate 1S (wafer) by the CVD method or the like and patterned by thelithography process and an etching step, thereby forming gate electrodesGHP, GHN, GLP1, GLN1, GLP2, GLN2 and FGS and flowing gate electrodes FG(gate electrode FGR and capacitive electrodes FGC1 and FGC2)simultaneously.

Next, as shown in FIGS. 33 and 34, n⁻-type semiconductor regions 20 aare simultaneously formed in the n channel type MIS•FET forming regionof the 6V device forming area of the low breakdown section by thelithography process and an ion implanting method or the like.

Subsequently, p⁻-type semiconductor regions 21 a, 17 a and 15 a aresimultaneously formed in the p channel type MIS•FET forming region ofthe 6V device forming area of the low breakdown section, a region forforming a capacitance section C and a region for forming a datawrite/erase charge injection/discharge section CWE by the lithographyprocess and the ion implanting method or the like.

Then, as shown in FIGS. 35 and 36, n⁻-type semiconductor regions 22 aand 12 a are simultaneously formed in the n channel type MIS•FET formingregion lying in the 1.5V device forming area of the low breakdownsection, a data read MIS•FETQR forming region and a selection MIS•FETQSforming region lying therein by the lithography process and the ionimplanting method or the like.

Here, the p-type semiconductor regions (the p-type hollow regions) areformed in addition to the introduction of an n-type impurity for formingthe n⁻-type semiconductor regions 22 a and 12 a. In such a case, ap-type impurity for forming the p-type hollow regions is introduced intothe neighborhoods (corresponding to substrate 1S's portions locatedbelow the gate electrodes GLN2, FGR and FGS) of the leading end portionson the channel side, of the n⁻-type semiconductor regions 22 a and 12 aof the substrate 1S from the direction diagonal to the first mainsurface of the substrate 1S, for example. Thus, a short channel effectcan suppressed or prevented at the n channel type MIS•FET and data readMIS•FETQR for the 1.5V device.

Subsequently, p⁻-type semiconductor regions 23 a are simultaneouslyformed in the p channel type MIS•FET forming region of the 1.5V deviceforming area of the low breakdown section by the lithography process andthe ion implanting method or the like.

Here, the n-type semiconductor regions (the n-type hollow regions) areformed in addition to the introduction of a p-type impurity for formingthe p⁻-type semiconductor regions 23 a. In such a case, an n-typeimpurity for forming the n-type hollow regions is introduced into theneighborhoods (corresponding to a substrate 1S's portion located belowthe gate electrode GLP2) of the leading end portions on the channelside, of the p⁻-type semiconductor regions 23 a of the substrate 1S fromthe direction diagonal to the first main surface of the substrate 1S,for example. Thus, a short channel effect can suppressed or prevented atthe p channel type MIS•FET for the 1.5V device.

Next, as shown in FIGS. 37 and 38, an insulating film constituted of,for example, silicon oxide is deposited over the first main surface ofthe substrate 1S by the CVD method or the like, followed by beingetch-backed using an anisotropic dry etching method, thereby formingsidewalls SW over their corresponding side surfaces of the gateelectrodes GHP, GHN, GLP1, GLN1, GLP2, GLN2, FGR and FGS and capacitiveelectrodes FGC1 and FGC2.

Subsequently, n⁺-type semiconductor regions 18 b, 20 b, 22 b and 12 bare simultaneously formed in their corresponding n channel type MIS•FETforming regions of the high breakdown section, low breakdown section,data read section and selection section by the lithography process andthe ion implanting method or the like. At this time, n⁺-typesemiconductor regions 25 for the above isolation are formedsimultaneously.

Subsequently to it, p⁺-type semiconductor regions 19 b, 21 b, 23 b, 15b, 17 b and 4 a are respectively formed in p channel type MIS•FETforming regions of the high breakdown section and the low breakdownsection, capacitance-section and write/erase charge injection/dischargeforming regions and a drawing region for the p-type well HPW3simultaneously by the lithography process and the ion implanting methodor the like.

Next, as shown in FIGS. 39 and 40, a silicide layer 5 a is selectivelyformed at part of the first main surface of the substrate 1S, the uppersurfaces of the gate electrodes GHP, GHN, GLP1, GLN1, GLP2 and GLN2 andresistive and capacitive electrode portions formed of polycrystallinesilicon or the like in accordance with a salicide process.

Prior to the step for forming the silicide layer 5 a, cap insulatinglayers 6 c are respectively formed so as to cover the upper surfaces ofthe floating gate electrodes FG (capacitive electrode FGC1, FGC2 andgate electrode FGR) and gate electrode FGS, the surfaces of thesidewalls SW and parts of the first main surface of the substrate 1Slying therearound. Thus, the silicide layer 5 a is prevented from beingformed over the upper surfaces of the floating gate electrodes FGcovered with the cap insulating layers 6 c.

A p channel type MIS•FETQHP and an n channel type MIS•FETQHN are formedat the high breakdown section in this way. p channel type MIS•FETQLP1and MIS•FETQLP2 and n channel type MIS•FETQLN1 and MIS•FETQLN2 areformed at the low breakdown section. Further, the capacitance section C,data write/erase charge injection/discharge section CWE and data readMIS•FETQR are formed in each memory cell forming area.

Subsequently, as shown in FIGS. 41 and 42, an insulating layer 6 aconstituted of, for example, silicon nitride is deposited over the firstmain surface of the substrate 1S (wafer) by the CVD method or the like.Thereafter, an insulating layer 6 b constituted of, for example, siliconoxide is deposited thereover thicker than the insulating layer 6 a bythe CVD method or the like. Afterwards, a chemical mechanical polishing(CMP) process is effected on the insulating layer 6 b to planarize theupper surface of the insulating layer 6 b.

Next, contact holes CT are formed in the insulating layer 6 by thelithography process and the etching process step. Subsequently, aconductor or conductive film constituted of, for example, tungsten (W)is deposited over the first main surface of the substrate 1S (wafer).Thereafter, it is polished by a CMP method or the like to formconductive or conductor parts 7 and 7 a through 7 g in the contact holesCT respectively. After their formation, the semiconductor device ismanufactured via the normal wiring forming step, inspecting step andassembling step.

According to the second embodiment, the constituent portions (parts) ofthe MIS•FETQHP, MIS•FETQHN, MIS•FETQLP1, MIS•FETQLP2, MIS•FETQLN1 andMIS•FETQLN2 for the LCD driver circuit, and the constituent portions(parts) of the capacitance section C, charge injection/discharge sectionCWE and MIS•FETQR and MIS•FETQS of each memory cell MC1 can be formedsimultaneously. Therefore, the process of manufacturing thesemiconductor device can be simplified. Thus, the time required tomanufacture the semiconductor device can be shortened. The cost of thesemiconductor device can be reduced.

Third Preferred Embodiment

FIG. 43 shows a plan view of a flash memory for a semiconductor deviceaccording to a third embodiment, FIG. 44 shows a fragmentary enlargedplan view of the flash memory shown in FIG. 43, and FIG. 45 shows across-sectional view taken along line Y3-Y3 of FIG. 43, respectively.Incidentally, although FIGS. 43 and 44 are plan views, parts thereof arehatched to make it easy to see the drawings. Cross-sectional views takenalong lines X1-X1, X2-X2 and X3-X3 of FIG. 44 are respectively identicalto FIGS. 22, 7 and 24.

In the third embodiment, the length (gate length) in a second directionX, of a capacitive electrode FGC1 of each charge injection/dischargesection CWE is longer than the length (gate length) in the seconddirection X, of each data read MIS•FETQR. In the third embodiment,constitutions other than it are identical to those described in thefirst and second embodiments.

Thus, in the third embodiment, the length in the second direction X, ofa second portion (gate electrode FGR) of a floating gate electrode FG,and the length in the second direction X, of a third portion (capacitiveelectrode FGC1) thereof can be changed (adjusted) according to need.

Fourth Preferred Embodiment

FIG. 46 shows, as one example, where a plurality of the memory cells MC0shown in FIG. 2 are arranged even in the first direction Y.Incidentally, although FIG. 46 is a plan view, parts thereof are hatchedto make it easy to see the figure. Cross-sectional views taken alonglines X1-X1, X2-X2 and X3-X3 of FIG. 46 are identical to those shown inFIGS. 6, 7 and 8 respectively.

The upper and lower memory cells MC0 shown in FIG. 46 are symmetricalwith respect to one another along the first direction Y (they are in amirror-inverted state). In the case of the layout of the memory cellsMC0, respective capacitance sections C of the upper and lower memorycells MC0 are arranged so as to face one another. It is howevernecessary to electrically insulate the capacitance sections C and C ofthe upper and lower memory cells MC0 from one another.

On the other hand, FIG. 47 is a plan view of a flash memory for asemiconductor device illustrative of a fourth embodiment, and FIG. 48 isa fragmentary enlarged plan view of the flash memory shown in FIG. 47.Incidentally, although FIGS. 47 and 48 are plan views, parts thereof arehatched to make it easy to see the drawings. Cross-sectional views takenalong lines X1-X1, X2-X2 and X3-X3 are identical to those shown in FIGS.6, 7 and 8.

Even in the fourth embodiment, memory cells MC1 located upward anddownward (in a first direction Y) as viewed in FIGS. 47 and 48 aresymmetrical with respect to one another along the first direction Y(held in a mirror-inverted state). In the fourth embodiment, however,data write/erase charge injection/discharge sections CWE of the memorycells MC1 located upward and downward (in the first direction Y) can beset so as to face one another by changing the layouts of respectiveelements of the memory cells MC1 as described above. Since, in thiscase, the charge injection/discharge sections CWE of the memory cellsMC1 located upward and downward (in the first direction Y) can be set tothe same potential, a p-type well HPW2 at which the chargeinjection/discharge sections CWE of the upper and lower memory cells MC1can be shared. Thus, since the adjoining space between the upper andlower memory cells MC1 can be closed up or reduced, the size in thefirst direction Y, of a memory cell array MR can be reduced or scaleddown as compared with the case of FIG. 46 (cell height can be reduced).Accordingly, the area of the memory cell array MR can be scaled down.Further, the storage capacity of a memory can be increased.

FIG. 49 is a plan view showing an arrangement of wirings in the memorycell array MR of FIG. 47. Incidentally, although FIG. 49 is a plan view,parts thereof are hatched to make it easy to see the drawing.

Each of wirings (including data write/erase bit lines WBL, data read bitlines RBL, etc.) extending along the first direction Y indicates a firstlayer wiring. Each of wirings (including control gate wirings CG, sourcelines SL and selection lines GS, etc.) extending along a seconddirection X indicates a second layer wiring. Symbol WSL indicates a wellpower-feeding wire or line.

Fifth Preferred Embodiment

FIG. 50 shows a plan view of a flash memory for a semiconductor deviceaccording to a fifth embodiment, FIG. 51 shows a fragmentary enlargedplan view of the flash memory shown in FIG. 50, FIG. 52 shows across-sectional view taken along line X4-X4 of FIG. 51, and FIG. 53shows a cross-sectional view taken along line X3-X3 of FIG. 51,respectively. Incidentally, although FIGS. 50 and 51 are plan views,parts thereof are hatched to make it easy to see the drawings. Across-sectional view taken along line X2-X2 of FIG. 51 is identical toFIG. 7.

In the fifth embodiment, dummy gates DG are disposed in theircorresponding space areas (areas for forming isolation parts TI) locatedover a first main surface of a substrate 1S of a memory cell array MR orthe like. The dummy gates DG are configured in consideration of theflatness of the upper surface of the insulating layer 6 and the layoutof repetition of patterns and are patterns electrically uncoupled toother portions in particular.

Providing such dummy gates DG makes it possible to enhance the flatnessof the upper surface of the insulating layer 6. Therefore, the accuracyof processing of wirings formed over the insulating layer 6 and contactholes CT defined in the insulating layer 6, for example can be enhanced.

The dummy gates DG are identical in configuration to the gate electrodeFGS of each selection MIS•FETQS referred to above. A silicide layer 5 ais formed over the upper surfaces of the dummy gates DG. Sidewalls SWare formed over their corresponding side surfaces of the dummy gates DG.

Such dummy gates DG are constituted of, for example, polycrystallinesilicon and simultaneously formed upon the step of forming the floatinggate electrodes FG, gate electrodes FGS and gate electrodes GLN1, GLN2,GLP1 and GLP2, etc. The silicide layers 5 a lying over the dummy gatesDG are also simultaneously formed upon a salicide step for forming thesilicide layers 5 a over the gate electrodes FGS and the like. Further,the sidewalls SW placed over the side surfaces of the dummy gates DG arealso simultaneously formed upon forming the sidewalls SW over the sidessurfaces of the gate electrodes FGS or the like. Thus, the number ofprocess steps for manufacturing the semiconductor device does notincrease even supposing that the dummy gates DG were provided.

Incidentally, a case in which the dummy gates DG are respectivelydisposed between active regions L2 and L4 and between the adjoiningp-type wells HPW2 adjacent to each other as viewed in the seconddirection X is illustrated by way of example here. However, the presentembodiment is not limited to it. The present embodiment is identical tothe fourth embodiment in configuration other that it.

Sixth Preferred Embodiment

FIG. 54 shows a plan view of a flash memory for a semiconductor deviceillustrative of a sixth embodiment, FIG. 55 shows a fragmentary enlargedplan view of the flash memory shown in FIG. 54, and FIG. 56 shows across-sectional view taken along line X5-X5 of FIG. 55, respectively.Incidentally, although FIGS. 54 and 55 are plan views, parts thereof arehatched to make it easy to see the drawings. Cross-sectional views takenalong lines X2-X2, X3-X3 and X4-X4 of FIG. 55 are identical to thoseshown in FIGS. 7, 53 and 52 respectively.

In the sixth embodiment, dummy active regions DL are disposed in free orspace areas (areas for forming isolation parts TI) lying over a firstmain surface of a substrate 1S of a memory cell array MR or the like.The dummy active regions DL are provided in consideration of flatness ofthe upper surface of an insulating layer 6 and are regions unformed withelements.

Providing such dummy active regions DL makes it possible to enhance theflatness of the upper surface of the insulating layer 6. Therefore, theaccuracy of processing of wirings formed over the insulating layer 6 andcontact holes CT defined in the insulating layer 6, for example can beenhanced.

The dummy active regions DL are identical to the active regions L. Thedummy active regions DL are formed simultaneously with the activeregions L. Thus, the number of process steps for manufacturing thesemiconductor device does not increase even supposing that the dummyactive regions DL were provided.

Incidentally, a case in which a plurality of the dummy active regions DLeach shaped in the form of a square as viewed in a plane are disposed isillustrated by way of example here. However, the present embodiment isnot limited to it. For instance, the plane shape of each dummy activeregion DL may be rectangular or made band-like. The present embodimentis identical to the fourth and fifth embodiments in configuration otherthat it.

Seventh Preferred Embodiment

A seventh embodiment will explain a case in which the memory cell arrayseach described in the second embodiment are disposed in two stages alonga first direction Y in a manner similar to the case described in thefourth embodiment. The seventh embodiment is identical to the second andfourth embodiments in configuration other that it.

FIG. 57 shows a plan view of a flash memory for a semiconductor deviceillustrative of a seventh embodiment, and FIG. 58 shows a fragmentaryenlarged plan view of the flash memory shown in FIG. 57, respectively.Incidentally, although FIGS. 57 and 58 are plan views, parts thereof arehatched to make it easy to see the drawings. Cross-sectional views takenalong lines X1-X1, X2-X2 and X3-X3 of FIG. 58 are identical to thoseshown in FIGS. 22, 23 and 24 respectively.

In the seventh embodiment, memory cells MC1 located upward and downward(in a first direction Y) shown in FIGS. 57 and 58 are symmetrical withrespect to each other (held in a mirror-inverted state) along the firstdirection Y in a manner similar to the fourth embodiment. Since chargeinjection/discharge sections CWE of the memory cells MC1 located upwardand downward (in the first direction Y) can be made equal in potentialin a manner similar to the fourth embodiment, a p-type well HPW2 atwhich the charge injection/discharge sections CWE of the upper and lowermemory cells MC1 can be shared. Thus, since the adjoining space betweenthe upper and lower memory cells MC1 can be closed up or reduced, thesize in the first direction Y, of the memory cell array MR can bereduced or scaled down as compared with the case of FIG. 46 (cell heightcan be reduced).

In the seventh embodiment, the p-type wells HPW2 of the chargeinjection/discharge sections CWE adjacent to each other along a seconddirection X are separated from each other by an n⁺-type semiconductorregion (n⁺-type diffusion layer) 25 formed between the adjoining p-typewells, within the memory cell array MR in a manner similar to the secondembodiment. Thus, since the adjoining space between the p-type wellsHPW2 and HPW2 adjacent to each other along the second direction X can benarrowed as compared with the case of the first embodiment, the size inthe second direction X, of the memory cell array MR can be reduced.

Thus, in the seventh embodiment, the area of the memory cell array MRcan be scaled down because both sizes in the first and second directionsY and X, of the memory cell array MR can be reduced. Further, thestorage capacity of a memory can be increased.

While the invention made above by the present inventors has beendescribed specifically on the basis of the preferred embodiments, thepresent invention is not limited to the embodiments referred to above.It is needless to say that various changes can be made thereto withoutthe scope not departing from the gist thereof.

For example, the p-type wells PW may be formed within the p-type wellsHPW1 and HPW2 of the capacitance sections C and the chargeinjection/discharge sections CWE. Thus, since the concentration of thep-type impurity at the substrate 1S's portions directly below thecapacitive electrodes FGC1 and FGC2 can be made high, depletion of thesubstrate 1S' portions directly below the capacitive electrodes FGC1 andFGC2 can be suppressed or prevented upon data rewriting (write/erase).Therefore, the rate of rewriting of data can be made fast because thevoltage applied to each of the capacitive insulating films 10 c and 10 dcan be made high.

In this case, the p-type wells PW lying within the p-type wells HPW1 andHPW2 in the flash memory area are simultaneously formed upon forming thep-type wells PW in the forming area of each n channel type MIS•FETQLN2at the low breakdown section in the LCD driver circuit area. Thus, thenumber of manufacturing process steps does not increase even supposingthat the p-type wells PW were formed within the p-type wells HPW1 andHPW2.

Each of the wells for the capacitance section C, chargeinjection/discharge section CWE, data read MIS•FETQR and selectionMIS•FETQS may be formed by the p-type semiconductor region PV of the pchannel type MIS•FETQHP at the high breakdown section in the LCD drivercircuit area. The p-type semiconductor regions PV for forming the wellsfor the capacitance section C, charge injection/discharge section CWE,data read MIS•FETQR and selection MIS•FETQS are simultaneously formedupon forming the p-type semiconductor region PV of each p channel typeMIS•FETQHP at the high breakdown section in the LCD driver circuit area.Since, in this case, the lithography process (a series of processes suchas resist application, exposure and development or the like, and a stepfor manufacturing a photomask used upon exposure) can be cut, the timerequired to fabricate the semiconductor device can be shortened.Further, the manufacturing cost of the semiconductor device can bereduced.

The p-type wells PW (or p-type wells HPW1 and HPW2) may be formed withinthe p-type semiconductor regions PV for forming the wells for thecapacitance sections C and the charge injection/discharge sections CWE.Thus, since the concentration of the p-type impurity of each of thesubstrate 1S' portions directly below the capacitive electrodes FGC1 andFGC2 of the capacitance section C and the charge injection/dischargesection CWE can be made high, the depletion of the substrate 1S'portions placed directly below the capacitive electrodes FGC1 and FGC2at data rewriting (write/erase) can be suppressed or prevented.Therefore, since the voltage applied to each of the capacitiveinsulating films 10 c and 10 d can be made high, the rate of rewritingof data can be made fast.

In this case, the p-type wells PW (or p-type wells HPW1 and HPW2) lyingwithin the p-type semiconductor regions PV of the capacitance section Cand the charge injection/discharge section CWE are simultaneously formedupon forming the p-type wells PW (or p-type well HPW4 in the region forforming each n channel type MIS•FETQLN1 at the low breakdown section) inthe region for forming each n channel type MIS•FETQLN2 at the lowbreakdown section in the LCD driver circuit area. Thus, the number ofmanufacturing process steps does not increase even supposing that thep-type wells PW (or p-type wells HPW1 and HPW2) were formed within thep-type semiconductor regions PV of the capacitance section C and thecharge injection/discharge section CWE.

While the above description has principally been made of the case inwhich the invention made by the present inventors is applied to thefabrication method of the semiconductor device that belongs to the fieldof application reaching the background of the invention, the presentinvention is not limited to it. The present invention can be applied invarious ways. The present invention can be applied even to, for example,a method of fabricating a micromachine. In this case, simple informationabout the micromachine can be stored by forming the flash memory in asemiconductor substrate formed with the micromachine.

The present invention can be applied to the manufacturing industry of asemiconductor device having a nonvolatile memory circuit section.

1-25. (canceled)
 26. A semiconductor device having a plurality ofnonvolatile memory cells, a high breakdown MISFET, and a low breakdownMISFET having a thinner gate insulating film than a gate insulating filmof the high breakdown MISFET, each of the memory cells including acontrol gate and a floating gate formed over a semiconductor substrate,the semiconductor device comprising: a capacitance section includingfirst impurity regions as control gate regions formed in thesemiconductor substrate and a first portion of the floating gate; a datawrite/erase charge injection/discharge section including second impurityregions formed in the semiconductor substrate and a second portion ofthe floating gate; and a data read MISFET including third impurityregions formed in the semiconductor substrate and a third portion of thefloating gate, wherein a plan area of the first portion of the floatinggate is greater than respective plan areas of the second and thirdportions, wherein structures of the third impurity regions are same asstructures of source and drain regions of the low breakdown MISFET,wherein each the source and drain regions of the low breakdown MISFEThas a first region of a first conductivity type, a second region of thefirst conductivity type having a higher impurity concentration than thefirst region, and a third region of a second conductivity type oppositeto the first conductivity type, and wherein the first, second and thirdregions are formed in a well region of the second conductivity typeformed in the semiconductor substrate and having a lower impurityconcentration than the third region.
 27. A semiconductor deviceaccording to the claim 26, wherein structures of the first and secondimpurity regions are different from structures of the third impurityregions.
 28. A semiconductor device according to the claim 26, whereinthe first and second regions are of the second conductivity type.
 29. Asemiconductor device according to the claim 28, wherein the firstconductivity type is an n type, and wherein the second conductivity typeis a p type.
 30. A semiconductor device according to the claim 26,including a plurality of said data read MISFETs, each associated with acorresponding one of the memory cells, wherein each of the memory cellsfurther comprises a selection MISFET which is adjacent to the associateddata read MISFET and which includes fourth impurity regions formed inthe semiconductor substrate and a first gate electrode, and whereinstructures of the fourth impurity regions are the same as structures ofsource and drain regions of the low breakdown MISFET.
 31. Asemiconductor device according to the claim 30, wherein structures ofthe first and second impurity regions are different from structures ofthe third and fourth impurity regions.